Willingham was selected by Florida out of the University of North Alabama in the 17th round of the 2000 amateur draft. After four seasons of bouncing around the Florida farm system, he made his Major League debut with the club in 2004.
In 2006, Willingham became the Marlins everyday left fielder, making quite an impact on the team by finishing up the season ninth in the NL Rookie of the Year balloting, having hit .277 with 26 home runs and 74 RBI in 142 games.
In 2007, Willingham appeared in 144 games for the Marlins, hitting .265 with 21 home runs and 89 RBI. For a total of three seasons, the right-hander roamed left field for the Marlins. He collected a total of 63 home runs and 219 RBI while hitting .266 in 416 games for Florida.
Willingham was traded along with Scott Olsen to the Washington Nationals for Jake Smolinski, P.J. Dean and Emilio Bonifacio and spent two seasons with the club.
He spent the 2011 season with the Oakland A's, winning the Catfish Hunter award, which honors the A's player whose play on the field and conduct in the clubhouse best exemplifies the courageous, competitive and inspirational spirit demonstrated by the late Hall of Fame pitcher.
Willingham recently signed a free agent contract with the Minnesota Twins.