When Christian was only six years old, his father began teaching him how to row in a flat-bottom boat tied to a clothesline on the Milwaukee River.

He began rowing more seriously his freshman year of high school, again coached by his father, after deciding that he "wasn't going to go anywhere in swimming".

[3] Ahrens stroked the gold medal winning United States men's eight at the 1997, 1998, and 1999 world championships, and was in the six seat for their fifth place 2000 Sydney Olympic boat.

Ahrens came out of retirement in 2004 to join the US Olympic squad in the three seat of the gold medal winning boat.

Ahrens retired from international rowing immediately upon crossing the finish line at the 2004 Olympics.