Michael Higdon volleyed the winner in the 73rd minute as Motherwell beat Celtic for the first time in exactly two years.
Chris Humphrey had opened the scoring prior to the break, before Georgios Samaras headed an equaliser for the visitors.
McFadden had come off the bench twice since re-signing for Motherwell, appearing in consecutive defeats against Dundee United and Ross County which had seen Motherwell slump from second to fourth place. But his first start since playing for Everton against Wolves on May 6 last year saw them return to second spot.
The former Everton man, who scored twice against Partick Thistle on his last start for Motherwell in August 2003, showed some neat skill in the centre circle as Motherwell made a bright start, but he left a 30-yard free-kick for Nicky Law, who curled a yard wide.
Motherwell took the lead in the 31st minute as Henrik Ojamaa laid the ball off to Keith Lasley who threaded it into the path of the onrushing Law. The midfielder turned centre-back Victor Wanyama inside and out before aiming a shot to the far corner. The effort beat Fraser Forster but would have gone wide had Humphrey not run in and finished off at the back post from close range.
Motherwell were almost caught out after their own corner when Anthony Stokes played Kris Commons through but Darren Randolph pushed him wide and Law came back to clear.
Celtic soon silenced the home support with a goal from nothing in the 63rd minute. James Forrest made space to cross from the byline on the right and Samaras seemed to catch out Randolph as he raced in to head inside the near post as the Irish goalkeeper came off his line to anticipate the ball dropping into his hands.
Wanyama was booked for hauling down McFadden, who came off and was replaced by Stuart Carswell in the 71st minute while Gary Hooper replaced Stokes, and Motherwell were back in front two minutes later.
Efe Ambrose and Adam Matthews got in each other's way at a high ball in the right-back position and Law broke down the left again following Ojamaa's pass. Law turned Ambrose and stood up a left-footed cross to the back post where Higdon arrived to cushion a volley into the roof of the net.