Craig Stammen attended the University of Dayton, where he made 60 pitching appearances over three seasons, as well as pitching in the Great Lakes Summer Collegiate League in 2004. He was an Atlantic 10 Conference Academic All-Conference pick in 2005, and was selected by the Washington Nationals in the twelfth round of the 2005 Major League Baseball Draft.
Stammen was assigned to the Vermont Expos of the short-season Single-A New York–Penn League where he made seven starts and six relief appearances, accruing an ERA of 4.06 while striking out 32 batters and allowing 12 walks and 62 hits over 51 innings. He started off the year in 2008 with the Triple-A Syracuse Chiefs, going 4–2 with a 1.80 ERA, and was called up to the major leagues on May 20, 2009. He had his first major league start May 21 versus the Pittsburgh Pirates.
In December 2016, Stammen signed a minor league contract with the San Diego Padres, and on March 30, 2017, he was added to the Padres’ 25-man active roster, where he joined the team as a reliever. He pitched 1.0 innings on April 3, his first major league appearance since April 14, 2015. He was effective throughout the season, posting an ERA of 3.15 in 80 1⁄3 innings. On January 7, 2018, he signed two-year contract with the Padres.