The Mexican international suffered a hernia injury and will undergo "minimally invasive" surgery Thursday, the MLS club announced Wednesday.
Dos Santos is expected to be sidelined for six weeks.
The 30-year-old entered the season with a groin injury that forced him to miss the Galaxy's opening match, but he managed to get 45 minutes under his belt before the league suspended the campaign in March due to the coronavirus pandemic.
Dos Santos ended last season with two goals and three assists in 29 regular-season appearances for Los Angeles.
The Galaxy will return to competitive action for the first time in over four months when they kick off their tournament campaign against the Portland Timbers on July 13.
The competition runs from July 8 to Aug. 11.