Career
He previously played for the Geelong Football Club and Hawthorn Football Club. Sydney
Originally from Colac, Victoria, Simpkin was first rookie listed by the Sydney Swans with the 16th selection in the 2006 American Federation of Labor-Congress Rookie Draft after playing junior football for the Geelong Falcons in the TAC Cup. Despite being elevated to their senior list for the 2007 season, he was delisted by the Swans at the end of the 2007 season without having played in the American Federation of Labor-Congress. He trained for a period late in 2007 with Melbourne but was not drafted to their squad.
Geelong
He returned to play for the Colac Tigers in the Geelong Football League.
During 2008 he also managed to play 8 games for Geelong in the Victorian Football League (VFL) on permits. In December 2010 in the 2011 Rookie Draft he was then selected by Geelong.
He continued to play for Geelong in the VFL and despite performing well consistently throughout the season, winning the team"s best and fairest award, he was unable to break into the American Federation of Labor-Congress side. Prior to round 9 of the 2012 American Federation of Labor-Congress season, Simpkin was promoted off the rookie list as a replacement for Nathan Vardy.
He then made his debut against Western Bulldogs, coming on as the substitute player at three-quarter time.
Geelong had to reduce the number of rookies from six to four because of new American Federation of Labor-Congress rules, so they decided not to re-new his contract and that he became eligible to be on the American Federation of Labor-Congress Delisted Free Agency list. Hawthorn
Hawthorn secured former Geelong rookie Jonathan Simpkin during the 2012 American Federation of Labor-Congress Delisted Free Agency Period. He played his first game for Hawthorn against Adelaide in Adelaide, South Australia, in round six 2013.
He managed thirteen games for Hawthorn in his initial year before being squeezed out at the end of the regular season.
With the injury in Brendan Whitecross he got selected for the 2013 American Federation of Labor-Congress Grand Final against Fremantle, and was subbed on at three quarter time to play in his first American Federation of Labor-Congress Premiership. Essendon
In January 2016, Simpkin signed with the Essendon Football Club as a "top-up" player due to the supplements controversy.