Muckalt was selected in the ninth round (221st overall) of the 1994 NHL Entry Draft by his hometown Vancouver Canucks. He played his first NHL game with the Canucks on October 12, 1998, against the Los Angeles Kings, notching his first NHL point as well, an assist. Muckalt scored his first NHL goal on October 20 against the Carolina Hurricanes. He played in 73 games during his rookie season, scoring 16 goals and 36 points. Muckalt was traded to the New York Islanders along with Dave Scatchard and goalie Kevin Weekes in exchange for goalie Felix Potvin and draft picks midway through the 1999–2000 season on December 19, 1999. Shortly after debuting with the Islanders, however, he was sidelined for the remainder of the season with a shoulder injury sustained in a game against the Tampa Bay Lightning on January 13, 2000. After a full season with the Islanders in 2000–01, he was involved in a blockbuster trade with the Ottawa Senators on June 23, 2001. Muckalt was dealt to Ottawa along with up-and-coming defenceman Zdeno Chara and the Islanders' first round pick in 2001 (which Ottawa would subsequently use to select Jason Spezza) in exchange for star centre Alexei Yashin.