The home run, the 534th of his career, tied Ramirez with Jimmie Foxx for 16th on the all-time list.
Ramirez was 0-for-2 in his next two at-bats before leaving the game in favor of Juan Pierre in the sixth.
Saturday was just Ramirez's second game back since finishing a 50-game suspension for violating MLB's drug policy.
In his first game back, Friday, Ramirez was 0-for-3 with a walk in the Dodgers 6-3 win.
Manager Joe Torre says he plans to continue to use Ramirez daily.
"We plan on playing him every day," Torre said. "If he comes in beat up, we'll alter the plan."
Torre also said of Ramirez's first inning home run: "[It will] take some pressure off."
Dodger fans, Manny is back!