The World Touring Car grid will expand to a season-high 25 cars for next weekend's final European round in Porto.
Campos will run three cars for the first time in 2013, with season regular Fernando Monje joined by both Hugo Valente and Nikolay Karamyshev.
Tom Boardman meanwhile will return to the WTCC fold after skipping the past two rounds in an attempt to fully fix his Special Tuning SEAT following a string of early technical woes.
Valente had been set to miss Porto as part of a six-round deal with the Spanish team, but is now able to compete given the team's expansion to three cars following Pepe Oriola's switch from SEAT to Chevrolet machinery.
Chevrolet dominated the WTCC's last event in Porto in 2011. Alain Menu and Rob Huff shared the victories, which Yvan Muller completing a race one podium lockout.