The sides agreed to the deal last week, and the Orioles said it was completed Monday after Wigginton completed a physical. He gets $2.5 million this year and $3.5 million in 2010.
The 31-year-old is expected to get some starts at first base and back up Melvin Mora at third base. He has also played second base, right field and left field in his seven-year career.
Wigginton batted .285 with 23 homers and 58 RBIs with the Houston Astros last season. A right-handed hitter, he has a .270 career average, 110 home runs and 384 RBIs in 784 games.
The Orioles designated infielder Scott Moore for assignment to make room for Wigginton on the 40-man roster.