Henn attended McLennan Community College in Texas, and was drafted in the 26th round in 2000 by the New York Yankees.

He played in Major League Baseball (MLB) for the Yankees, San Diego Padres, Minnesota Twins, Baltimore Orioles and New York Mets.

On May 4, he started in the majors in place of Randy Johnson against the Tampa Bay Devil Rays.

In his third major league outing, which came against the New York Mets, Henn allowed six run on seven hits in four innings.

The roster opening left by Henn's demotion allowed the Yankees to call up Kevin Reese.

[8] He was charged with the loss in two pivotal, extra inning games with direct playoff implications against the Angels and Tigers in late August 2007.

The Twins called him up on May 19 to fill the roster position left open by Glen Perkins being placed on the disabled list.