The Surbiton-based business will continue to operate under the "Verve" name, as a unit within Omnicom Media Group.
Verve’s team spans 14 nationalities and provides services in 15 languages. It was founded in 2009 by chief executive Lisa Myers. Clients include Expedia, Sage, Go Compare and Made.
It has developed proprietary technologies including the "Link score tool", which allows links to be evaluated. and was named "Large SEO agency of the year" at The European Search Awards 2017.
Colin Gottlieb, Omnicom Media Group EMEA’s chief executive, said: "A successful acquisition enhances an enterprise across three critical areas — capabilities, clients and culture. Verve Search hits the mark on all three measures, and will be another valuable specialist resource to drive business results for our clients."
Myers said the deal would allow her business to continue to follow its "vision to be the destination for digital pioneers".
She added: "Omnicom is a great fit for Verve, in terms of both culture and vision. We are passionate about innovation and creativity, and becoming part of the Omnicom family will allow us to grow further."
Verve has produced a video explaining a bit about the business: