Before playing the NHL, Plekanec played two seasons with HC Kladno of the Czech Extraliga. He was drafted by the Montreal Canadiens with the 71st overall pick in the 2001 NHL Entry Draft. He played two seasons with their affiliate in the American Hockey League (AHL), Hamilton Bulldogs. He played two games and then stayed in Hamilton for a third AHL season because of the 2004–05 NHL lockout. Since the 2005-06 NHL season, he has been part of the Canadiens.