Leetch was born in Corpus Christi, Texas, but was raised in Cheshire, Connecticut, where his family moved when he was three months old.

As a sophomore, Leetch's 90 mph fastball helped the Cheshire Rams baseball team to a state championship and, as a senior at Avon Old Farms, he set the school record for strikeouts in a game with 19.

NHL scouts were starting to take notice and the New York Rangers chose Leetch as their first-round pick (9th overall) in 1986, making him the first player drafted that year who did not play major junior hockey.

[3] After one season at Boston College, he played for the US Olympic team at the 1988 Games in Calgary, making his NHL debut, eight days later, with the New York Rangers on February 29, 1988, versus St. Louis.

As the Rangers slowly developed into a championship-caliber team, Leetch won increasing respect from fans for his quiet demeanor and entertaining, offensive-minded play.

That year, the Rangers' 54-year championship drought ended with a seven-game Stanley Cup Finals victory over the Vancouver Canucks.

Leetch became the first non-Canadian to be awarded the Conn Smythe Trophy, and remained the only American to do so until Tim Thomas of the Boston Bruins in 2011.

In 1997, he again won the Norris Trophy and the Rangers made a surprise run to the Eastern Conference Finals, where they were defeated by the Philadelphia Flyers.

[5] On June 30, 2003, as a pending free agent, his rights were traded to the Edmonton Oilers in exchange for Jussi Markkanen and a fourth-round pick in the 2004 draft.

Leetch was set to play the 2004–05 season with the Maple Leafs; however, due to the 2004–05 lockout, the last year of his contract expired, and he became a free agent.

[12][13] On January 24, 2008, the New York Rangers retired Leetch's number 2 jersey, joining fellow 1994 Stanley Cup Champion teammates Mark Messier and Mike Richter, as well as Rod Gilbert and Eddie Giacomin in the rafters of Madison Square Garden.