Leonard was drafted with the 11th overall pick by the Portland Trail Blazers in the 2012 NBA draft. On July 13 he signed his rookie scale contract with the Trail Blazers. On October 31, 2012, Leonard made his NBA debut, logging 23 minutes and scoring four points against the Los Angeles Lakers. He made his first career start on November 21, 2012, against the Phoenix Suns, finishing with 12 points and 5 rebounds. On March 30, 2013, he had a season-best game with 22 points and 10 rebounds in a loss to the Golden State Warriors.