The British comedy, which is released by Entertainment Film Distributors and stars local favourite Simon Pegg, fell by 22% this weekend and boasted a sturdy $6,083 (£3,008) site average.
Universal Pictures International (UPI) saw Atonement maintain steady progress - the romantic World War II drama, starring Keira Knightley and James McAvoy, climbed back up to second place despite falling 16%. It generated $2.35m (£1.16m) from 424 sites in its third weekend for a $13.6m total to date in the territory.
New entry I Now Pronounce You Chuck And Larry, also released by UPI, opened at number three in the UK chart. The Adam Sandler comedy, which has amassed nearly $120m in the US, generated $2.2m (£1.1m) from 408 sites for a $5,407 (£2.674) site average.
US teen sensation Superbad, written by Seth Rogan (of Knocked Up fame) and Evan Goldberg, dropped by 28% in its second weekend to number four. The comedy, distributed by Sony Pictures Releasing International (SPRI), took $2.15m (£1.06m) from 402 sites and has generated $6.9m (£3.4m) to date.
UPI had its third film in the UK top five this weekend with The Bourne Ultimatum - the third instalment of the franchise took $1.1m (£562,099) from 318 sites over the three-day period. It has generated more than $45m in the territory after six weeks on release.
Quentin Tarantino's part of the Grindhouse collaboration, Death Proof, opened to number six this weekend and failed to cross the $1m mark. The thriller, released by Momentum Pictures, generated $824,115 (£407,525) from 286 screens in its first weekend.
Paramount Pictures International's (PPI) thriller Disturbia, starring Shia LaBoeuf (of Transformers), dropped two places to number seven, grossing $683,998 (£338,232) from 373 sites in its second weekend.
UPI's Knocked Up still remained in the top 10, despite a 44% drop over the weekend. The Judd Apatow comedy generated $519,697 (£256,990) from 259 sites in its fifth weekend. It boasts a $16.02m tally to date.
Lionsgate's 3:10 To Yuma failed to cross the $500,000 mark again in its second weekend. The Western remake starring Russell Crowe and Christian Bale fell 44% with a $419,988 (£207,684) take at the weekend.
Entertainment's action adventure Shoot 'Em Up fell 54% at the weekend to number 10 taking $349,331 (£172,744) from 274 sites for a $1.5m tally to date.
PPI's Angelina Jolie drama A Mighty Heart failed to make the UK top 10 in its opening weekend while Punjabi film Mitti Wajan Maardi, from Think Big Entertainment, boasted the highest site average at $6,654 (£3,295) per site.
The top 20 films in the UK generated $14.75m from the period of September 21-23 and were collectively up 25.6% compared to the same period last year.
For the full UK chart go to global box office on screendaily.com.