The sitcom spinoff, starring Simon Bird, Joe Thomas, James Buckley and Blake Harrison, remains at the chart summit and has recorded the biggest live-action comedy opening ever in the UK with £20 million.
The total surpasses the £17 million earned by The Hangover Part II earlier this year and puts The Inbetweeners Movie's total at £27.7 million.
Anne Hathaway and Jim Sturgess's romantic drama One Day debuts in second place with £2.2 million, while Rise of the Planet of Apes charts at number three and The Smurfs holds its spot at number four.
Elsewhere, new releases Final Destination 5 and Conan the Barbarian make the top ten, bowing at number five and number eight respectively.
The UK weekend box office top ten in full:
1. (1) The Inbetweeners Movie - £5,696,848
2. (-) One Day - £2,208,724
3. (2) Rise of the Planet of the Apes - £1,659,572
4. (4) The Smurfs - £1,478,650
5. (-) Final Destination 5 - £1,450,464
6. (3) Cowboys & Aliens - £792,898
7. (5) Harry Potter and the Deathly Hallows: Part 2 - £765,191
8. (-) Conan the Barbarian - £622,268
9. (6) Spy Kids: All the Time in the World - £607,051
10. (8) Mr Popper's Penguins - £408,985
Watch the stars of The Inbetweeners Movie answer questions from a stuffed beaver below: