The short answer is scope. An SEO company specializes in one channel: organic search. A digital marketing agency is a generalist that usually covers organic search alongside several other channels, such as paid advertising, social media, email marketing, and sometimes design or web development. Both can help your website attract customers, but they are built around different ranges of work, and the right choice depends on what your business needs right now.
What an SEO company focuses on
An SEO company concentrates on improving how your site performs in unpaid search results. That work typically includes technical fixes to how your site is built and crawled, keyword research, content aimed at search demand, on-page optimization, and earning links from other sites. Because the whole team works in this one area every day, the depth of expertise tends to be higher. Staff are more likely to follow search algorithm changes closely and understand the specific ranking factors that move organic traffic.
The tradeoff is that organic search is the main lever an SEO company pulls. If your goals also depend on paid ads, social campaigns, or email, an SEO company may not handle those directly, and you would coordinate that work separately.
What a digital marketing agency covers
A digital marketing agency works across multiple channels under one roof. A single agency might run your paid search and social ads, manage email campaigns, produce social content, and handle SEO as one part of a broader plan. The advantage is breadth and coordination. One team plans the channels together, so your messaging stays consistent and you manage one relationship instead of several.
The tradeoff is depth. A generalist agency employs specialists in different areas, but the SEO capability inside a full-service agency is not always as deep as the capability inside a dedicated SEO company. Some digital marketing agencies have strong SEO teams; others treat it as a smaller line item. If organic search is central to your goals, it is worth asking specifically how the agency staffs and approaches SEO rather than assuming it is a strength.
Specialist versus full-service: the tradeoffs
A specialist gives you concentrated skill in a narrow area and is well suited to solving a defined problem. A full-service agency gives you coverage and convenience but spreads its attention across many disciplines.
Using several specialists at once has its own cost. If your SEO, ads, and content are handled by separate providers, you become responsible for keeping them aligned, sharing information between them, and resolving conflicts when their recommendations differ. That coordination takes real time.
When each one fits
A digital marketing agency tends to fit when you do not yet have a marketing system in place and need several channels built and running together, or when you want one partner to scale with you as you grow. It also fits when paid channels and short-term results matter as much as long-term organic growth.
An SEO company tends to fit when your other marketing is already working but your organic search performance has stalled, or when search visibility is the specific problem you want solved. A focused team is well positioned to find the technical bottleneck, content gap, or authority weakness holding rankings back.
Many established businesses use both. They rely on a digital marketing agency or in-house team for the broad program and bring in an SEO company for depth in organic search. If you do this, define clear ownership for each area so the two efforts support each other instead of overlapping.
How to decide
Start with the problem you are trying to solve. If you need a full marketing program built and managed, lean toward a digital marketing agency. If you need real depth in organic search, lean toward an SEO company. Then check the details: ask either type of provider exactly which services they deliver in-house, how they staff the work, and how they report results. The label on the door matters less than the actual scope of work and the strength of the team behind it.