Media Buying Agencies: What They Do for Your Ad Spend

A media buying agency plans, negotiates, and purchases advertising placements on behalf of a brand, across channels like paid search, programmatic display, connected TV, audio, and out-of-home. They sit between the advertiser and the media owner, and their core job is to get the right inventory at the right price, in the right context, at the right time.

That sounds straightforward. In practice, it is one of the most commercially consequential decisions a marketing team can make, and one of the least well understood outside of the people who do it every day.

What a Media Buying Agency Actually Does

Strip away the jargon and a media buying agency does four things. It plans where your money should go. It negotiates the cost of getting it there. It executes the buy and manages the placements. And it reports back on what happened.

The planning piece is where genuine expertise lives. A good media buyer understands audience behaviour across channels, knows where attention is cheap relative to its value, and can model reach and frequency against a budget in a way that most in-house teams cannot, simply because they lack the cross-client data to benchmark against. When I was running an agency that managed significant ad spend across dozens of clients simultaneously, the pattern recognition that came from that breadth was genuinely difficult to replicate in a single-brand environment.

The negotiation piece is where agencies earn disproportionate value, or fail to. Large agencies carry buying power that individual advertisers cannot match. A media owner will give a holding-company agency preferential rates, added value, and first-look inventory access that a direct buyer simply will not get. That leverage is real, and it is one of the strongest arguments for using an agency rather than going direct.

Execution and reporting are table stakes. Any competent agency should be able to traffic a campaign, manage pacing, and pull a performance report. If an agency is selling you on its reporting capabilities as a differentiator, that is a sign they do not have much else to sell.

If you want a broader view of how paid media fits into your acquisition strategy, the paid advertising hub covers the full landscape, from channel selection to budget allocation to what the industry consistently gets wrong.

The Conflict of Interest Nobody Talks About Clearly Enough

Most media buying agencies are compensated as a percentage of media spend. That is the dominant model, and it creates a structural misalignment that every advertiser should understand before signing a contract.

If your agency earns 10% of whatever you spend, they earn more when you spend more. That does not mean every recommendation to increase budget is wrong. Sometimes it genuinely is the right call. But it does mean you should scrutinise budget recommendations with that incentive in mind, and you should ask whether the agency would make the same recommendation if they were paid a flat retainer.

There is also the question of rebates and volume bonuses from media owners. Large agencies negotiate volume deals with publishers and platforms, and some of that value gets passed back to clients, while some does not. The industry has made progress on transparency here, but it has not been solved. When I was on the agency side, I saw how opaque some of these arrangements could be, even internally. Clients who never asked about it rarely found out.

This is not an argument against using a media buying agency. It is an argument for going in with clear eyes. Ask about compensation structure. Ask how the agency makes money beyond the management fee. Ask whether they have preferred partnerships with specific platforms or publishers, and what that means for your media plan.

Programmatic Has Changed the Game, But Not in the Way Most People Think

The rise of programmatic advertising, and the self-serve interfaces that came with it, created a narrative that media buying was being commoditised. If anyone can log into Google Ads or Meta Ads Manager and buy media directly, what exactly is an agency for?

The answer is that accessibility and effectiveness are different things. Yes, the platforms are accessible. But knowing how to structure a campaign, how to set bidding strategies that align with actual business objectives rather than platform-optimised proxies, how to read cost-per-click data in context rather than in isolation, and how to avoid the common traps that platforms quietly profit from, that is where expertise still matters enormously.

I have seen brands hand six-figure monthly budgets to in-house teams with six months of experience, because they assumed the platform UI was intuitive enough to compensate for the knowledge gap. The platform is intuitive. The strategy behind it is not. The results reflected that distinction clearly.

Programmatic has also introduced a new layer of complexity around brand safety, viewability, and ad fraud that did not exist in the same way when media buying meant calling a TV rep or booking a print page. A media buying agency that operates at scale has data on which inventory sources perform and which inflate metrics without delivering real business outcomes. That intelligence is worth paying for, if the agency is willing to share it transparently.

The Moz blog has a useful piece on running better Google Ads campaigns with AI that gets into some of the practical complexity around modern paid search management. It is a good illustration of how much the craft has evolved even within a single channel.

Full-Service vs Specialist: Which Model Fits Your Business

There are broadly two types of media buying agency. Full-service agencies handle planning and buying across all channels, often alongside creative, strategy, and sometimes performance marketing. Specialist agencies focus on a single channel or a narrow cluster, such as programmatic display, paid search, or connected TV.

The full-service model has advantages in coordination. When the same team is responsible for paid search, paid social, and programmatic, there is less chance of channels cannibalising each other, and the reporting tends to give a more coherent picture of what is driving results. The disadvantage is that full-service agencies often have uneven depth. They may be excellent at one channel and adequate at others, and the client rarely knows which is which until the results come in.

Specialist agencies tend to have deeper technical expertise within their lane. A pure-play paid search agency will typically have more sophisticated bidding strategies, better keyword architecture, and more nuanced understanding of quality score mechanics than a generalist agency managing search as one of ten channels. The tradeoff is integration. If your paid search agency and your paid social agency are not talking to each other, you will almost certainly end up with attribution confusion and duplicated effort.

The right answer depends on your business stage and internal capability. Early-stage brands with limited in-house resource often benefit from a single coordinated partner, even if that partner is not the deepest specialist in every channel. Mature advertisers with sophisticated in-house teams often get better results from specialists in each channel, with strong internal coordination to tie it together.

One thing worth noting: the agency model is not the only option. For some channels, particularly paid search, an in-house team with the right training can outperform an agency, simply because they have deeper knowledge of the product and the customer. Unbounce has written about how client-side factors can undermine PPC performance, and it is a useful reminder that the agency is rarely the only variable in the equation.

What Good Media Planning Looks Like in Practice

Good media planning starts with a business problem, not a channel. That sounds obvious, and yet most media plans I have reviewed over the years start with a budget and a channel mix, and work backwards to justify it.

When I was at lastminute.com, we launched a paid search campaign for a music festival that generated six figures of revenue within roughly a day. The campaign was not complicated. What made it work was that we understood the purchase window precisely, we knew the search behaviour of the audience, and we matched the creative and the landing page to the intent of the query. The media buy itself was relatively straightforward. The thinking behind it was not.

That experience shaped how I think about media planning. The question is never “which channels should we be on?” The question is “where is our audience, when are they ready to act, and what do we need to say to them at that moment?” The channel selection follows from that, not the other way around.

A media buying agency that starts a planning conversation by presenting a channel mix without first understanding your customer’s decision experience is doing it backwards. It may still produce reasonable results, because the channels they recommend are probably sensible defaults for your category. But it will not produce the kind of results that come from genuinely insight-led planning.

The integration of paid and organic thinking matters here too. Moz has covered SEO and PPC integration in depth, and the core principle applies to media planning more broadly: channels do not operate in isolation, and a plan that treats them as independent levers will consistently underperform one that accounts for how they interact.

How to Evaluate a Media Buying Agency Before You Sign

Most agency pitches are theatre. I have sat on both sides of the pitch table, and I know how much effort goes into making a pitch feel compelling, regardless of whether the underlying capability is there. Here is what to look for beyond the deck.

Ask to see a media plan they built for a comparable client, with the client’s permission. Not a sanitised case study with the numbers removed. An actual plan, with rationale, channel allocation, and the thinking behind it. If they cannot or will not show you that, they are selling you on presentation skills, not planning capability.

Ask who will actually work on your account. In large agencies, the senior people who present in the pitch are often not the people who manage the account day to day. This is not unique to media agencies, but it is particularly consequential in media buying, where the quality of day-to-day decisions directly affects spend efficiency. Get the names and meet the team before you sign.

Ask about data access. Will you own the platform accounts? Will you have direct access to the data, or will you be dependent on the agency’s reporting layer? Owning your own platform accounts is non-negotiable. If an agency insists on holding the accounts in their name, walk away. You will be starting from scratch if you ever want to move.

Ask about their approach to testing. A media buying agency that is not running structured tests, whether on creative, audience, bidding strategy, or placement, is managing spend rather than improving it. Testing should be built into the operating model, not treated as an optional extra.

And ask about their relationship with the platforms. Agencies with formal partnerships with Google, Meta, and the major programmatic platforms often get early access to beta features and dedicated support. That is genuinely useful. But it also means they have a commercial relationship with the platforms whose inventory they are recommending. That is not a disqualifier, but it is worth understanding.

The Innovation Trap in Media Buying

Every few years, a new format or channel gets positioned as the next big thing in media buying. Connected TV, digital out-of-home, retail media, audio, influencer-led paid media. Some of these are genuinely valuable. Some are interesting experiments. And some are agency revenue diversification dressed up as client opportunity.

I have judged the Effie Awards, which means I have read hundreds of campaign submissions from agencies making the case that their work drove real business results. The ones that stand out are almost never the ones built around novel formats. They are the ones built around a clear understanding of the customer, a sharp creative idea, and disciplined media planning. The channel is usually fairly conventional.

When an agency pitches you on a new format, the question to ask is not “is this interesting?” The question is “what specific business problem does this solve that our current channel mix does not?” If the answer involves words like “brand building” or “future-proofing” without any accompanying measurement framework, you are probably being sold innovation for its own sake.

That is not to say new formats are never worth testing. Influencer marketing integrated with paid media distribution is a good example of a genuinely useful evolution, where the creative authenticity of influencer content is amplified through paid targeting rather than relying entirely on organic reach. Later has a useful overview of how influencer marketing and paid media work together that is worth reading if you are considering that approach.

The point is not to avoid new formats. It is to evaluate them against a real business problem rather than against the agency’s enthusiasm for them.

What Separates a Good Agency Relationship from a Bad One

In my experience managing agency relationships from the client side and running agencies from the inside, the quality of the relationship is the single biggest predictor of results, more than the agency’s size, their technology stack, or their award history.

Good relationships have a few things in common. The client shares business context, not just campaign briefs. The agency asks questions that go beyond the brief. There is a shared definition of what success looks like, tied to business outcomes rather than media metrics. And there is enough trust on both sides to have honest conversations when things are not working.

Bad relationships tend to look like this: the client treats the agency as a vendor and withholds commercial context. The agency produces work that technically meets the brief but does not move the business. Both sides blame the other when results disappoint. And the relationship limps along for another year because switching costs feel high.

When I was growing an agency from a small team to over a hundred people, the clients who got the best work were almost always the ones who treated the relationship as a genuine partnership. They shared data. They gave honest feedback. They pushed back when something did not make sense. That kind of engagement makes agencies better, because it gives them the information and the accountability they need to do good work.

If you are looking for a broader framework for thinking about paid media investment, the paid advertising section of The Marketing Juice covers the strategic decisions that sit above channel and agency selection, including how to think about budget allocation and what paid media consistently gets wrong.

When to Bring Media Buying In-House

The in-housing trend accelerated significantly over the past decade, driven partly by a desire for more control over data and partly by a genuine belief that in-house teams could outperform agencies on cost efficiency. The reality is more nuanced.

In-housing works well when you have a dominant channel that requires deep, consistent expertise, such as a brand that does most of its acquisition through paid search and has the volume to justify a dedicated specialist. It works less well when you need breadth across multiple channels, because building genuine expertise across paid search, programmatic, paid social, and connected TV in a single in-house team is expensive and difficult to sustain.

The talent problem is real. Good media buyers are in demand, and the best ones often prefer agency environments because of the variety of work and the career development opportunities. An in-house role managing a single brand’s media can feel limiting after a few years, and turnover in in-house media teams is often underestimated as a cost.

A hybrid model often makes more sense than a binary choice. Keep strategic oversight and data ownership in-house. Use an agency for execution, buying power, and channel-specific depth. That structure gives you the control and transparency of in-housing without sacrificing the scale advantages that agencies bring.

About the Author

Keith Lacy is a marketing strategist and former agency CEO with 20+ years of experience across agency leadership, performance marketing, and commercial strategy. He writes The Marketing Juice to cut through the noise and share what works.

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