Becoming a starter near the end of his freshman year at Illinois under head coach Ron Turner, Kittner became one of the most prolific passers in Illinois history. He ended his tenure at Illinois as the school's all-time leader in career passing attempts (1,264), career passing touchdowns (70), passing touchdowns in a single season (27), and victories as a quarterback (24). Kittner wrapped up his collegiate career only 3 yards shy of Jack Trudeau's Illini record for all time passing yards. Entering his senior year, Kurt was considered a possible Heisman candidate. Kittner and receiver Brandon Lloyd led Illinois' offense as the Fighting Illini finished with a 7–1 record in the Big Ten and won their first Big Ten championship in 11 years on their way to a berth in the 2002 Sugar Bowl. Kittner's last collegiate game ended in a 47–34 loss against the LSU Tigers.
Kittner was drafted in the 5th round of the 2002 NFL Draft by the Atlanta Falcons. He saw no action in his rookie year, being third-string quarterback behind Doug Johnson and 2001 first overall pick, Michael Vick. In 2003, after a preseason injury sidelined Vick and ineffective play caused second-string quarterback Doug Johnson to be benched, Kittner saw his first regular season action. Playing in seven games (four of which he started), he threw for 391 yards, scoring 2 touchdowns and throwing 6 interceptions. The highlight was a 27–7 win over the New York Giants at Giants Stadium where Kittner threw for a touchdown. The Falcons ended the season however with a 5–11 record.
In 2005, Kittner was invited to training camp with the Chicago Bears and coach Turner, then offensive coordinator for Chicago. He earned a roster spot as the third-string quarterback. After starter Rex Grossman was injured in camp, journeyman Jeff Blake was brought in to back up rookie starter Kyle Orton, leaving Kittner at third string. When Grossman returned from injury on November 23, 2005, Kittner was released without playing a regular season down for the Bears.
Kittner holds the NFL record for most pass attempts in a career without a fumble (114).
Kittner currently resides in Chicago with his wife Leila Cehajic, a former University of Illinois tennis player. He works for Jones Lang LaSalle in Chicago doing commercial real estate. In July 2007, Kittner was named the color analyst for University of Illinois football radio broadcasts, replacing long-time analyst Jim Grabowski.