Both businesses are based in London. Spot's staff will move into Threepipe's offices next week. The Spot brand will be phased out. The two firms had worked together on mutual clients over the past year.
Spot was founded in 2014 by Tony Thomas, who becomes a shareholder in Threepipe and will join its board, alongside co-founder Jim Hawker, and Farhad Koodoruth.
Koodoruth was the founder of Blowfish Digital, which was bought by Threepipe in 2013. Hawker's other co-founder, Eddie May, today launched a new creative comms offering at Hanover.
Hawker said the addition of SEO capabilities was crucial for an industry moving away from print-focused media.
"PR agencies have delivered SEO impact more by accident than by design and for a long time now people have considered the PR industry to have failed to really grasp the potential that SEO knowledge can deliver to clients," he said.
The combined business has 60 staff and clients include Reiss, Sweaty Betty, Oracle and Campari. In addition to PR, Threepipe has paid search, display marketing, social commerce and content marketing capabilities.
Spot Digital’s video seeding offering will continue to operate as an independent business.