Rex Kern was recruited by legendary football coach Woody Hayes to play for Ohio State Buckeyes. In his four seasons playing for the Buckeyes his team compiled a record of 27-2. During this time the team was led by a quality sophomore class, known as the Super Sophomores, which Kern is commonly referred to as the leader.

In 1968, Kern led the Buckeyes to a national championship following an undefeated season and a 27-16 victory over the University of Southern California Trojans, led by Heisman trophy winner O.J. Simpson. Kern led the Buckeyes back to the national title game in 1970, however this time in a losing effort.

In 1971, Kern was drafted by the Baltimore Colts. He played three NFL seasons in Baltimore as a cornerback before being traded to the Buffalo Bills. After one season with Buffalo he retired. Brother Kern has his PhD from Ohio State University in education.