The 20-year-old lined up for the Owls' Under-21s on Monday, four days after his Elland Road release.
The 20-year-old was named in the Owls' lineup to face Birmingham City this afternoon and played the full 90 minutes in a 1-1 draw at Solihull Motors.
Parkin, who was on Leeds' books for 14 years prior to his departure by mutual consent, signed his first professional contract in 2013 but failed to break into the first-team picture at Elland Road.
Confirming his exit on Twitter, Parkin said he was "now looking forward to the next chapter in my career".
If everything goes to plan, it could be down the road at Wednesday, for whom Leeds' 2014 apprentice of the year Luke Booker now plays.
Booker, who signed for the Owls last summer, appeared alongside his former teammate for 60 minutes, having replaced Sean Clare midway through the first half.
Meanwhile, Tottenham Hotspur midfielder Charlie Hayford played his third game in a week for Neil Thompson's team, but there was no sign of Chelsea's Kevin Wright, who'd featured in their two previous fixtures.
Left-back Wright scored the only goal in Tuesday's win against Huddersfield.