The 20-year-old has featured nine times for the Eagles in all competitions and has also enjoyed a loan spell at Barnet during the latter stages of the 2010/11 campaign, making eight appearances.
Equally adept at left-midfield or left-back, Parsons offers manager Gary Waddock cover for Sam Wood who is expected to miss six to eight weeks with a knee injury.
Parsons becomes the Chairboys' second signing in quick succession following the arrival of Watford defender Adam Thompson on loan.
Boss Gary Waddock told the club's official website: "We've been watching him for a while. He's an attacking full-back, but with Sam Wood out injured we may play him one position further forward.
"He's a very positive player, is direct and will give us another option on the left."