After the 1900 Olympic Games, Kraenzlein retired from athletic competition in late 1900, as the owner of six world and four Olympic records. He came back to Milwaukee and started a dental practice. Kraenzlein also became a manager of the Milwaukee Athletic Association. In 1902, having returned to Philadelphia, he married Claudine Gilman, whom he knew from the student days. He practiced dentistry in Philadelphia till 1906 when he became the track-and-field coach at Mercersburg Academy, a selective prep school in Pennsylvania. Amongst his students was Ralph Craig, a future Olympic titleholder in both the 100 and 200 metres in 1912 Olympic Games.