The feature film adaptation of E4's popular sitcom, starring Simon Bird, Joe Thomas, James Buckley and Blake Harrison, banks more than £13 million from 455 screens across the UK to coast past its big-budget competition.
The Inbetweeners Movie's debut weekend, including previews on Wednesday and Thursday, makes it the biggest opening of all time for a UK comedy.
Bridget Jones: Edge of Reason (£10.43 million), Wallace & Gromit: Curse of the Were-Rabbit (£9.37m), Mamma Mia! (£6.59m) and Mr Bean's Holiday (£6.44m) follow the The Inbetweeners Movie in the UK all-time list.
Producer Chris Young said of the movie's success: "We are thrilled that The Inbetweeners Movie is the biggest opening of all time for a UK comedy. We really want to thank all the cinemagoers out there who have made the film such a huge success."
Elsewhere, Western/sci-fi mash-up Cowboys & Aliens makes a disappointing UK debut as it lands at number three behind Rise of the Planet of the Apes.
The UK box office top ten in full:
1. (-) The Inbetweeners Movie - £13,216,736
2. (1) Rise of the Planet of the Apes - £2,425,887
3. (-) Cowboys & Aliens - £1,777,320
4. (2) The Smurfs - £1,445,619
5. (3) Harry Potter and the Deathly Hallows: Part 2 - £959,001
6. (-) Spy Kids: All the Time in the World - £703,078
7. (4) Super 8 - £441,675
8. (5) Mr Popper's Penguins - £421,312
9. (-) Glee: The 3D Concert Movie - £356,271
10. (7) Cars 2 - £311,454
Watch Digital Spy's interview with the stars of The Inbetweeners Movie below: