The lawsuit was filed in San Diego Superior Court on Dec. 5 and reported Tuesday by the San Diego Union-Tribune.
Cheri Olvera alleges Giles began abusing her in 2002. The lawsuit accuses him of hitting and slapping her in the face, shaking and kicking her, and battering her twice when she was pregnant with Giles' child.
Giles' agent, Joe Bick, told the Union-Tribune he would not comment.
Padres spokesman Warren Miller said the team was aware of the lawsuit and declined further comment.