Etten attended Villanova University and was drafted by the Athletics from the Oakland Oaksminor league team. He made his major league debut with the Athletics late in 1938, also playing part-time for them in 1939. After playing two seasons with the Phillies, he was traded to the Yankees in January 1943, and he responded by leading the American League with 22 home runs, and drawing 97 walks in 1944, and with 111 RBIs the following season, also best in the league. During his four-year stint with the Yankees, Etten also ranked among league leaders in most offensive categories, was a member of the 1943 World Champion team, and was selected to the All-Star Game in 1945. In 1947, he appeared in fourteen games for the Phillies before retiring.
In a nine-season career, Etten was a .277 hitter with 89 home runs and 526 RBIs. Playing every inning of his career as a first baseman, he recorded a .988 fielding percentage.
