Moseley (1-3) hurled seven scoreless innings, scattering three hits and two walks and fanning six.
The former New York Yankees right-hander, signed to a one-year deal in the off-season, didn't allow a runner to reach third base while earning his first win as a Padre.
Brad Hawpe highlighted a three-run second inning with a two-run single and Chase Headley drove in a pair with a ninth-inning double for San Diego, which took the rubber match of a three-game set at Dodger Stadium.
Los Angeles starter Jon Garland (1-2) was saddled with the loss. He walked four batters and allowed three hits for three runs over six frames.
Matt Kemp went 2-for-4 for the Dodgers.