He played junior hockey for the Peterborough Petes and was selected 65th overall by the Pittsburgh Penguins in the 1972 NHL Amateur Draft. Lalonde turned pro with the Hershey Bears in 1972-73 and then made the Penguins in the following season.
In the middle of the 1974-75 Lalonde was traded to the Washington Capitals for Lew Morrison. He played five seasons for the Capitals until he was sent down to the minors in 1978-79. Lalonde completed his career in Austria with HC Salzburg and retired in 1981.
In the NHL Lalonde played in 397 games and scored 45 goals and 78 assists.