Howlett was selected by Essendon with pick 30 in the 2010 rookie draft, as a 21-year-old from Peel Thunder in the West Australian Football League.

His final season with Peel Thunder saw him claim the club's best and fairest award.

He and his teammates were initially found not guilty in March 2015 by the AFL Anti-Doping Tribunal,[2] but a guilty verdict was returned in January 2016 after an appeal by the World Anti-Doping Agency.

[4] He returned home to WA and signed with the club he was originally drafted from, Peel Thunder in the WAFL, for the 2018 season.

[6] In Round 9 of the 2021 WAFL season Howlett played his 100th[7] game for Peel Thunder against Swan Districts before announcing his retirement from WAFL footy at the end of that season.