Devine joins Porta from MHP Communications, where he was chief executive.
He is expected to oversee the continued integration of the group, Porta said in a statement. The company also highlighted that Devine brings significant experience given his record at MHP where he successfully integrated three agencies.
David Wright, Porta chief executive, said: "Gavin is our second senior hire in less than six months. We are building a significant integrated consultancy that has the specialist expertise necessary to service the communications needs of major organisations under one roof.
“Gavin's appointment will help us to build on the considerable progress that we have already made in building an integrated offer and winning more blue chip clients."