Curnow returned to Victoria, and signed up with Box Hill in the VFL in 2009. Curnow's 2009 season was solid, but his 2010 season was exceptional, and he was consistently Box Hill's best player. His season was cut short when he broke his leg in Round 13, missing the Hawks' last eight games; nevertheless, he had already polled enough votes to win the Box Hill Best and Fairest (the Col Austen Trophy), and he finished third in the J. J. Liston Trophy, after holding a comfortable lead at the time of his injury. Curnow played a total of 33 senior games for Box Hill during his two years at the club, and also played one representative game for the VFL.
Following his successful VFL season, Curnow was recruited back to the AFL by the Carlton Football Club with its first selection in the 2011 AFL Rookie Draft (#18 overall). He was given guernsey number 35. After impressing in the pre-season, Curnow became the club's nominated rookie, and he made his debut for the Blues in the club's first round match. He was one of Carlton's best players in the first six matches of the season, but suffered a shoulder injury in Round 7; although he didn't miss much football with the injury, he did not regain that strong form for the rest of the season.