The contract depends upon Wigginton passing a physical, two people familiar with the agreement said Tuesday, speaking on condition of anonymity because the deal was not final.
Wigginton's agreement was first reported by The Sun and foxsports.com.
The 31-year-old batted .285 with 23 homers and 58 RBIs with the Houston Astros last season. A right-handed hitter, Wigginton has a .270 career average, 110 home runs and 384 RBIs in 784 games.
Wigginton played third base and left field last season, but has also played first base, second base and right field. His signing likely means Kevin Millar's three-year run with the Orioles has likely ended.
He is also expected to back up Melvin Mora at third base.
Wigginton made his major league debut in 2002 with the New York Mets. He played with Pittsburgh in 2004 and 2005, then spent the next two seasons with Tampa Bay before being traded to the Astros on July 28, 2007, for pitcher Dan Wheeler.
The 6-foot, 225-pounder missed most of April last season with a broken left thumb but returned to play in 111 games with Houston.
His best season was in 2006, when he batted .275 with 24 homers and 79 RBIs for Tampa Bay.