On August 2, 2010, Hellickson made his major league debut against Minnesota Twins. During his debut, he held the Twins to two runs over seven innings. He struck out six while walking two. He was optioned back to the Triple-A Durham Bulls after the start. He was once again recalled to the majors on August 10 to take the spot of Wade Davis in the rotation. He made his second career start that day against the Detroit Tigers at Comerica Park, earning his second career victory after pitching seven shutout innings with three hits, seven strikeouts and no walks as the Rays won 8–0.
On August 21, 2010, Hellickson was optioned to the High-A Charlotte Stone Crabs to work on moving to the bullpen. He was recalled to Tampa Bay on September 1, and made his first appearance out of the bullpen on September 4, pitching 1 and 2/3 innings giving up 2 runs.
Hellickson was optioned to Charlotte on August 27. He was recalled from the Double-A Montgomery Biscuits on September 3 after the major league rosters expanded. He did not pitch for either minor league team.