He attracted notice from professional scouts due to his NHL draft eligibility, and was selected to play for Team Orr at the 2010 CHL Top Prospects Game.

During the Warriors' seven-game playoff series against the eventual WHL champions, the Calgary Hitmen, McIlrath played every game and recorded an assist.

On March 17, 2011, McIlrath signed his first National Hockey League (NHL) contract with the New York Rangers, the team that drafted him 10th overall in 2010.

[8] After a strong pre-season showing, McIlrath was named to the full 23-man roster on October 2, 2015,[citation needed] and on December 15, scored his first NHL goal.

His most notable fight of the season was on Valentine's Day against Philadelphia Flyers forward Wayne Simmonds, who had punched and concussed Rangers' captain Ryan McDonagh in an earlier (February 6, 2016) game between the two teams.

[10] McIlrath had a poor training camp in 2016 and spent the early part of the 2016–17 season as a reserve defenceman, only making one appearance with the team before he was placed on waivers on October 27.

[11] He was reassigned to play four games in the AHL with the Hartford Wolf Pack before he was traded by the Rangers to the Florida Panthers in exchange for Steven Kampfer and a conditional seventh-round pick on November 8, 2016.