Growth as a Service, or GaaS, is a service-business model in which an outside firm — usually a marketing, growth, or experimentation agency — sells ongoing growth outcomes (acquisition, activation, retention) rather than discrete deliverables (a campaign, a creative asset, a strategy document) to a client company.
The model emerged in the 2010s as an extension of the "growth hacking" function inside startups: an agency offered on a retainer or performance-based fee to embed with a client and run the experimentation, channel testing, and conversion-rate work that an in-house team would otherwise do. Compared to traditional agency engagements, GaaS contracts tend to be longer, tied to metrics rather than scope, and built around shared dashboards, weekly sprints, and embedded operators.
The category sits inside the broader X-as-a-Service ecosystem alongside more familiar entries (SaaS, PaaS, IaaS) and shares their economic premise: convert what was previously a hire or a one-off project into a recurring service.