Harshal Patel was sold to  Royal Challengers Bangalore for 10.75 crores at the mega auction in Bengaluru. In the 2012 IPL auction, Patel was bought by the Royal Challengers Bangalore. In January 2018, Patel was bought by the Delhi Daredevils (now Delhi Capitals) in the 2018 IPL auction. In January 2021, Patel was traded by the Delhi Capitals to the Royal Challengers Bangalore prior to the fourteenth season of IPL.

On 9 April 2021, in the first match of IPL 2021 while playing for the Royal Challengers Bangalore, Patel took 5 wicket-haul (5-27) against the Mumbai Indians. Harshal Patel is first bowler to claim a 5-wicket haul against Mumbai Indians in IPL.This is his best bowling figures in the IPL and he also became the first ever player to take a 5 wicket-haul against the Mumbai Indians in the IPL. His 5 wicket-haul also became the third best bowling figures by an uncapped Indian player in the IPL.