In baseball, he was selected by the Kansas City Athletics, and was offered basketball scholarships to UCLA, North Carolina, and Ohio University.

The 1968 team shut out top-ranked Purdue on October 12 and went on to an undefeated season, a Big Ten championship, and a berth in the Rose Bowl.

Kern was named Most Outstanding Player in the bowl as Ohio State defeated O. J. Simpson and the USC Trojans, 27–16, and were consensus national champions.

Despite the loss, Ohio State finished as Big Ten co-champions with Michigan and Kern was third in balloting for the 1969 Heisman Trophy.

Kern was the Colts' National Football League Players Association (NFLPA) representative during the union's strike prior to the 1974 season.

After the strike ended, he was waived when Baltimore general manager Joe Thomas acted on his threat to cut players who had walked out.

Kern played eight games with the Buffalo Bills that season before ending his career as an active player due to chronic back problems.