He played in eleven seasons of the National Hockey League (NHL) for the Pittsburgh Penguins, Columbus Blue Jackets, Edmonton Oilers and Winnipeg Jets.

He appeared in three regular and two playoff games with the Wilkes-Barre/Scranton Penguins, Pittsburgh's American Hockey League (AHL) affiliate, when he joined the team at the end of the 2006–07 season.

[5] He appeared in his first Stanley Cup playoff game in the Penguins' second round series against the Montreal Canadiens on May 4 when he replaced the injured Staal as the third-line centre between Tyler Kennedy and Matt Cooke.

[6] In Game 5 on May 8, Letestu recorded his first Stanley Cup playoff point with an assist on a second period goal by Sergei Gonchar.

After scoring against the Chicago Blackhawks during pre-season, Letestu said, "I worked hard this summer... the praise is nice but it's only as good as your last game.

After three-and-a-half seasons with the Blue Jackets, Letestu left the club as a free agent on July 1, 2015, after signing a three-year contract with the Edmonton Oilers.

[14] Later that day, Letestu was traded from Nashville to the Blue Jackets in exchange for a fourth-round pick in the 2018 NHL Entry Draft.

On August 14, 2018, Letestu agreed to attend the Florida Panthers' training camp on a professional try-out (PTO) contract.

[19] Having left the Blue Jackets as a free agent, on July 2, 2019, Letestu signed a one-year, two-way contract with the Winnipeg Jets.