Trumbo was selected by the Anaheim Angels in the 18th round (533rd overall) of the 2004 Major League Baseball Draft. He was promoted to the major leagues as part of the September roster expansions on September 3, 2010. He made his major league debut on September 11, 2010 as a pinch hitter for Mike Napoli and then remained in the game to play first base.
Trumbo entered the 2011 season looking for some early-season playing time at first base after an excellent spring in which he displayed his prodigious power. Trumbo hit his first career home run on April 12, 2011, off Fausto Carmona of the Cleveland Indians. Although he planned to be a stopgap until Kendry Morales' returned from injury, he became the Angels' full-time first baseman for the 2011 season due to Morales' season-ending surgery.\ He led all rookies with 29 home runs and 87 RBIs while batting .254 in his rookie campaign, but finished second in Rookie of the Year voting to Jeremy Hellickson of the Tampa Bay Rays. Trumbo also led the American League in putouts with 1,284 in 2011.
The Angels acquired Albert Pujols on December 8, 2011, which forced Trumbo to change positions. In the early stages of the 2012 season Trumbo and Alberto Callaspo shared time at third base; Trumbo has since started games in left and right fields as well as designated hitter.
On June 10, 2012, Trumbo had a career-high six RBIs on two three-run home runs in a game against the Colorado Rockies. Trumbo was selected for the 2012 Home Run Derby by AL captain Robinson Cano, advancing to the second round before being ousted in a playoff by Jose Bautista. Trumbo was selected to the 2012 Major League Baseball All-Star Game in his sophomore season. It is the first of his career.
- Career statistics and player information from MLB, or Baseball-Reference, or The Baseball Cube
- Baseball Almanac