The Montreal, QC native starred in the Quebec Midget AAA Hockey League with Laval before joining the QMJHL's Laval Titan in 1993-94. Chosen 105th overall by the Washington Capitals in the 1995 NHL Entry Draft, Gratton went on to play parts of three seasons with the Titan before being acquired by the Granby Predateurs during the 1995-96 season.
An offensively gifted forward, Gratton was instrumental in leading Granby to the 1996 Memorial Cup title. Comming off his Memorial Cup win, Gratton made his professional debut with Washington's AHL affiliate in Portland in 1996-97. Over the course of the next two seasons, Gratton continued to hone his skills in Portland, while seeing limited action with Washington.
After three seasons with the Capitals organization, Gratton was traded to the Calgary Flames in the summer of 1999. Upon his arrival with the Flames, Gratton went on to spend the majority of the season with the club's AHL affiliate in Saint John, and the better part of the following season as well before claimed on waivers by the Montreal Canadiens in the spring of 2001.
Since his arrival with the Canadiens organization, the former QMJHL junior has continued to share his time between the NHL and the AHL.