Jean-Joel Perrier Doumbe grabbed an 84th-minute winner to clinch a 34th Scottish Cup - and the Double - for Celtic against Dunfermline at Hampden.
Perrier Doumbe celebrates his winner with Paul Hartley
The Cameroonian knocked home from close range from Craig Beattie's pass to finally end the Pars resistance, as the SPL champions toiled for long periods.
Jan Vennegoor of Hesselink and Kenny Miller both went close for Celtic in a mainly stuffy game.
Dunfermline worked hard but failed to test Celtic goalkeeper Arthur Boruc.
Neil Lennon was captaining Celtic for the last time before leaving the club after almost seven years service.
And team-mate Steven Pressley was looking to create a record by winning the cup with three different clubs after having picked up medals with Rangers and Hearts.
Celtic manager Gordon Strachan sprung a selection surprise when Perrier Doumbe was preferred to Gary Caldwell at right-back, while Jan Vennegoor of Hesselink was partnered in attack by Kenny Miller.
Dunfermline - who lost their recent battle to remain in the SPL - came to Glasgow minus four regulars.
Tom McManus and Stephen Glass were both cup-tied, Gary Mason was suspended and midfielder Jim O'Brien, on loan from Celtic, was barred from playing.
Former Celt Mark Burchill was chosen by Pars manager Stephen Kenny to feature alongside Jim McIntyre - who scored the semi-final winner against Hibernian - in attack.
The Fifers belied their relegated status and started positively, going close in the third minute when Burchill screwed a left-footed shot from 12 yards across goal and wide following a link-up with McIntyre.
The busy Burchill had a penalty claim minutes later, falling down following a challenge from Paul Hartley, but referee Kenny Clark ignored his plea.
Celtic's Shunsuke Nakamura takes on Scott Morrison
There was an early nervousness from Celtic, although they did have the ball in the net after 21 minutes when midfielder Shunsuke Nakamura had the ball in the net but Hartley had fouled Pars keeper Dorus de Vries.
The Glasgow side should have taken the lead on the half-hour following an intelligent build up.
Miller turned delightfully on the right and his precise cross was met by Vennegoor of Hesselink, but the former PSV Eindhoven man somehow sent his diving header past the post.
it was the closest either team came to breaking the deadlock in the first-half, and Celtic were having problems finding a way past a well-organised Pars defence.
Dunfermline's Scott Morrison did try his luck from distance as half-time approached, but his left-foot shot skidded a yard past the target.
Certainly, the Pars went into the break fully realising they had a chance to win against the subdued Celts.
But Celtic began the second half in positive fashion and, in the 51st minute when Aiden McGeady supplied a cross from the left for the incoming Miller, a goal looked certain.
However, the Scotland striker's header from six yards was too close to De Vries and Dunfermline survived.
Miller paid the price when he was replaced four minutes later by Craig Beattie, as Strachan opted to freshen up the attack.
After 61 minutes, Celtic full-back Lee Naylor brought the best from De Vries, firing in a right-foot shot which the Dutchman did well to gather.
Lennon was surprisingly replaced by Caldwell, and the Hoops captain appeared extremely dejected by Strachan's decision, with the contest remaining open.
Kenny sent on Stevie Crawford for Morrison, hoping the veteran forward could lift his side, with chances scarce at either end.
Substitute Beattie almost put Celtic ahead in the 79th minute, but he was unlucky to stroke an angled effort inches wide, after charging beyond the Pars rearguard from Nakamura's raking pass down the right.
The East End Park outfit defended well, but found themselves tiring towards the end.
And they failed to prevent Perrier Doumbe from emerging as an unlikely cup winning hero, when the Cameroon international picked up a return pass from Beattie in the danger zone to stab the ball home with just six minutes remaining.
It was enough to seal Dunfermline's fate, as Celtic added the cup to their SPL title.
Celtic: Boruc, Perrier Doumbe, McManus, Pressley, Naylor, Nakamura, Lennon (Caldwell 66), Hartley, McGeady, Miller (Beattie 56), Vennegoor of Hesselink. Subs Not Used: McGovern, Riordan, Bjarnason.
Booked: McGeady, Perrier Doumbe, Pressley.
Goal: Perrier Doumbe 85.
Dunfermline: De Vries, Shields, Wilson, Bamba, Muirhead, Scott Morrison (Crawford 72), Young, McCunnie, Hammill, Burchill (Williamson 89), McIntyre (Hamilton 80). Subs Not Used: McKenzie, McGuire.
Ref: K Clark