The Costa Rican international has arrived in Italy for a medical which will take place on Thursday, and is set to sign a three-year deal with Frosinone.
Campbell has been at Arsenal for seven years - although there were at first problems with a work permit - and has featured 23 times in the Premier League for the 'Gunners', scoring three goals.
The 26-year-old has had loan spells all over Europe, most recently with Real Betis, though previously with Sporting Lisbon, Villarreal, Olympiacos and Lorient.
Joel Campbell also featured in Costa Rica's 2018 World Cup squad, though he was sent home in the group stage in what was a disappointing tournament for 'Los Ticos'.