Dentsu Aegis Network has agreed to acquire one of the largest independent search and content marketing agencies not affiliated with the major agency holding companies.

Terms of the deal and billings were not disclosed, but the companies said San Diego-based Covario has a staff of more than 140 people.

Covario’s stand-alone search software unit, Rio SEO, will remain independent following the sale of the agency operations to Dentsu Aegis.

Rio SEO has raised additional funding from FTV Capital, Dubilier & Co., Voyager Capital, and Stratim Capital, and said Dema Zlotin, one of the original founders of Covario, will be joining the company as CEO.

The deal is expected to close in the fourth quarter and Covario’s agency business will become part of the Dentsu Aegis network, ultimately becoming integrated into Dentsu Aegis existing digital unit iProspect. Covario co-CEOs Michael Gullaksen and Jeff Johnson will have “key senior executive positions in the combined Covario / iProspect organization,” the companies said.

“We have a very clear strategy for the capabilities and agencies we bring into our operating model,” Nigel Morris, CEO of Dentsu Aegis Network Americas & EMEA, said in a statement, adding: “Covario is uniquely suited to complement and scale iProspect’s outstanding offering as the world’s leading digital performance agency.”

Covario three-peated as OMMA magazine’s “Search Agency of the Year” in 2011, 2012 and 2013.

Originally posted at MediaPost.