Jon Tiomkin was born in Brooklyn on July 12, 1979, and now lives in New York City. Tiomkin is a graduate of St. John's University.
Tiomkin took up fencing as a freshman in high school and defeated the captain of the team on the first day of practice.
He was the American foil champion in 1999 and 2003. He won the team gold and individual silver (losing to Dan Kellner) at the 2003 Pan Am Games. Tiomkin finished second at the 2004 Nationals to Kellner.
His best individual result at worlds was 64th in 2001 and 2003, and his best team result was ninth in 2003.
He made his Olympic debut in Athens in individual and team foil. Jon faced Maher Ben Aziza of Tunisia in the first round (the round of 64) of the 2004 Olympic individual foil event. The Tunisian scored the first two touches but Timokin bounced back to win 15-10. Unfortunately the American fell apart in the round of 32 against the number one seed, Andrea Cassara of Italy and lost 3-15.
Timokin was a member of the U.S foil team as well, along with Dan Kellner. They beat Germany 45-43 in the quarterfinals, as Jon lost his first match-up 5-6 to Andre Wessels, won his second against Peter Joppich 5-1, as well as winning his third vs. Ralf Bissdorf 5-4. The U.S was brushed aside by a superior Chinese team 45-35 in the semis, but Timokin was the most impressive American throughout the encounter. He beat Haibin Wang 7-3, lost 3-5 to Zhaozhi Dong and outscored Hanxiong Wu 7-5. The U.S.A missed out on the bronze medal as they lost the decider 45-38 to Russia. Once again Jon was very solid as he outmaneuvered Yuri Moltchan 5-4 and beat Renal Ganeev 7-4 before succumbing to Viatcheslav Pozdniakov 3-5.
Tiomkin has kept a journal noting every bout he fenced over the last eight years, in practice and competition.