The Sheffield United loanee's first-half strike kept Gary Rowett's side hard on the heels of the top three in the race for an automatic promotion spot.
But it dealt a blow to Argyle's hopes of sneaking into a play-off spot with John Sheridan's men now five points adrift.
Burton could have been more than a goal to the good after dominating the first half.
Billy Kee had a 25-yard shot tipped over by Jake Cole before the goalkeeper breathed a sigh of relief when a Jimmy Phillips show was deflected onto a post.
Home full-back Damien McCrory also saw a free-kick skim the crossbar as well as forcing Cole to make a diving save.
Burton's pressure paid dividends in the 26th minute when McFadzean steered in a 10-yard shot after a mistake by Neal Trotman.
The visitors came to life after the break but Reuben Reid's shot was deflected the wrong side of the post and Conor Hourihane could only shoot into the arms of keeper Rob Lainton.
Substitute Michael Symes sliced wide a chance to double Burton's lead nine minutes from the end.