The player joins after seven seasons with Toronto FC. He will reunite with former head coach Gregg Vanney, who led Toronto and Zavaleta when the squad won the the MLS Cup, Supporters' Shield and Canadian Championship treble in 2017.
"Eriq is an experienced defender who brings more leadership and championship pedigree to our back line. We welcome him to the team and look forward to integrating him into the group," Vanney said in a statement.
Zavaleta first kicked off his professional career in 2015, joining the Seattle Sounders after being selected 10th overall by the Western Conference giants. He spent two seasons there, before featuring for Chivas USA and Toronto FC.
The defender has registered two goals and one assist in 140 regular-season games across nine seasons in Major League Soccer.
"Eriq has a wealth of experience in MLS and signing him provides important depth to our roster," said Galaxy technical director Jovan Kirovski in a release.
Internationally, Zavaleta has become a regular for El Salvador, making 15 appearances for Los Cuscatlecos since his debut in 2021.
The Galaxy has seen a fantastic start to their 2022 season, recording two consecutive victories as Mexican nationals Chicharito and Efrain Alvarez lead the goal chart. The team returns to the pitch on Saturday against the Seattle Sounders.