Hibs emphatically clinched their first win in seven Scottish Premier League matches in the clash at Fir Park to rise to fifth in the table, while 'Well drop to ninth.
John Rankin gave Hibs a sixth-minute lead and they quickly recovered from losing the lead to Bob Malcolm's superb 42nd-minute free-kick as Dean Shiels (50) and Fletcher (61) struck early in the second half.
Motherwell goalkeper Graeme Smith had kept the score down but he was beaten in the last minute by Derek Riordan.
Hibs, who brought back goalkeeper Yves Ma-Kalambay and right-back David van Zanten, dominated from the start.
Smith's first save came in the second minute when he stood up well to palm away Riordan's attempt to dink the ball home.
Fletcher, who overcame the ankle injury that kept him out of Scotland's defeat by Argentina, had put Riordan clean through after Malcolm gifted him possession well inside his own half.
Well were in disarray and Rankin had already shot just over after a slick break before scoring in the sixth minute. The midfielder ran past Malcolm and shot low into the bottom corner from 20 yards.
Hibs had another good chance as Riordan's cross following a short corner found Sol Bamba in space eight yards out but the midfielder headed well over.
Motherwell had recalled striker Chris Porter and right-winger Jamie Murphy but they were struggling to string passes together, and Smith saved again from Riordan after his defence had been exposed in the 21st minute.
Fletcher headed on Ian Murray's lofted ball and Riordan beat the offside trap but the former Celtic player's low strike came off Smith's legs.
Motherwell finally began to force Hibs back but still could not pass their way through and Ma-Kalambay comfortably held two long-range free-kicks from Malcolm.
Hibs always looked dangerous on the break with front pair Riordan and Fletcher playing on Motherwell's advanced back line.
But it was third time lucky for Malcolm in the 42nd minute when he curled a brilliant 20-yard free-kick into the top corner after Rob Jones had been penalised for leaning on Porter.
Hibs took less than five minutes of the second half to restore their lead though after again stretching the home defence.
Shiels ran on to Fletcher's lay-off and finished impressively into the bottom corner from 16 yards.
The visitors easily soaked up a spell of pressure and Fletcher struck a memorable goal in the 61st minute.
Stephen Hughes halted Murray's overlap but the ball broke for the striker 30 yards out and he blasted it first time into the bottom corner.
Ma-Kalambay tipped over a powerful snapshot from John Sutton moments later but Smith was soon tested with another 30-yard strike, this time grabbing Bamba's effort at the second attempt as Riordan tried to pounce.
The home side brought on wingers Jim O'Brien and Darren Smith but still lacked the spark to break down Hibs.
Hibs looked dangerous whenever they went forward and Shiels lobbed the ball on to the crossbar after flicking it over a defender.
Riordan also threatened a spectacular goal but his volley looped just past the far post from a tight angle.
Smith again saved Motherwell's blushes with a double stop from substitute Colin Nish and Rankin.
Ma-Kalambay touched the unmarked O'Brien's header wide in a rare Motherwell chance but Hibs went straight up the park and notched a fourth.
The home defence backed off Riordan and he struck low into the net past Smith's outstretched hand.