Tkaczuk was born in Toronto, Ontario. As a youth, he played in the 1993 Quebec International Pee-Wee Hockey Tournament with Toronto Marlboros minor ice hockey team.

He was selected sixth overall in the 1997 NHL Entry Draft by the Calgary Flames. He represented Canada at the 1999 World Junior Ice Hockey Championships, where he won a silver medal and led the team in scoring. Tkaczuk was named to the American Hockey League’s All-Rookie Team the following season. He played in the National Hockey League for the Calgary Flames during the 2001–02 campaign, but returned to the minors and never saw NHL action again.

Tkaczuk left the Flames system at the end of 2000–01 after winning the Calder Cup when traded along with Fred Brathwaite, Sergei Varlamov, and a 2001 ninth-round pick to the St. Louis Blues for goaltender Roman Turek on June 23, 2001. He would then play two more years in the AHL for the Worcester IceCats and after being released by the St. Louis Blues, for the Bridgeport Sound Tigers.

In 2006, Tkaczuk signed for ERC Ingolstadt of the DEL. In 2007, he moved to EV Duisburg Die Füchse and played there until the completion of the 2008–09 season. Tkaczuk was second in goals during the 2007–08 season (17).

After six years abroad, Tkaczuk returned to North America and signed with the Charlotte Checkers of the ECHL on November 13, 2009. He would later be loaned to the Rochester Americans on December 7, 2009. On January 6, 2010, the Hartford Wolf Pack signed Tkaczuk to a professional tryout (PTO) contract. Tkaczuk finished the season with 45 points in 46 games for the Checkers.

In the following season, Tkaczuk signed a one-year contract with the EC TREND-Dornbirn of the second-tier Austrian National League on September 16, 2010 After scoring 33 points in 26 games with Trend, Tkaczuk signed for the Nottingham Panthers of the Elite Ice Hockey League (EIHL) in the United Kingdom, on January 19, 2011.

After retiring, he became an assistant coach with the Owen Sound Attack and the Kitchener Rangers of the OHL. He then became assistant coach of the American Hockey League’s Chicago Wolves in 2016 before spending the 2017–18 season as skills coach with the St. Louis Blues. In 2018, he became an assistant coach for the Blues’ AHL affiliate the San Antonio Rampage.