Tom Saintfiet’s side defended doggedly to keep out the Eagles of Carthage, who missed a penalty and lost Mohamed Drager to a red card late on before Ablie Jallow stunned them with the winner in the dying moments of the game.
The Scorpions finished runners-up to Mali in their group and will face Guinea in the round of 16, while Tunisia must contend with Group D winners Nigeria.
Mondher Kebaier’s men bossed proceedings in the first half with almost 75 per cent of the possession as the Gambians sat back and absorbed a tonne of pressure.
The West Africans struggled up front due to the final pass letting them down, although an early chance saw Musa Barrow clear the target by some distance with an ambitious long-range strike on the left in the sixth minute.
Ali Abdi had the first sniff at goal for Tunisia on the quarter-hour mark when he latched onto a ball over the top and made his way into the box on the left before getting off a shot that was deflected wide off Omar Colley.
Hamza Rafia should have done better with their next opportunity on 34 minutes, but he directed a free header well wide of the right post from a cross on the right.
Rafia went closer five minutes later after being played in by Seifeddine Jaziri on the left, though the Standard Liege midfielder could only find the side-netting from a tight angle.
Barrow attempted the spectacular on 36 minutes as he connected with a long ball over the top and sent a first-time shot on the turn well over the crossbar from outside the box.
Baboucarr Gaye was relieved to see a firm strike from Ellyes Skhiri go wide of the left post via a deflection on 41 minutes and the Gambia goalkeeper was called into action moments later to push away Aissa Laidouni’s shot from outside the box.
However, the referee quickly pointed to the spot when Modou Jagne fouled Jaziri on the follow-up.
The Zamalek forward took the penalty himself, but Gaye was equal to the task as he guessed the right way to make the save.
Barrow drew a routine save out of Bechir Ben Said from a free-kick on the left in stoppage-time, while Anis Ben Slimane cleared the target with a set-piece of his own shortly after the restart.
The woodwork came to the North Africans’ rescue six minutes later when Barrow curled a sumptuous free-kick against the crossbar, while at the other end of the pitch Hannibal side-footed an effort straight at Gaye from the edge of the area on 79 minutes.
Drager was sent off in stoppage time for a second bookable offence and Gambia struck moments later to snatch all three points.
Jallow chested down a cross from the left and smashed his shot past Ben Said at his near post to send their fans inside the stadium into delirium.
Gambia (0) 1 (A.
Tunisia (0) 0
Gambia:Gaye, Janko (Badamosi 62′), Sonko-Sundberg (Touray 61′), Gomez, O.
Colley, Jagne, Musa Barrow, Bobb, Mbye (A.
Jallow 46′), Sohna (Adams 46′), Modou Barrow.
Tunisia:Ben Said, Abdi, Talbi, Ifa, Mathlouthi (Drager 57′), Skhiri, Laidouni, Ben Slimane, Khaoui (Msakni 57′), Jaziri, Rafia (Hannibal 68′).
Gambia subdues Tunisia with last-gasp goal