Grossing an estimated $29m, the talking-dog family comedy was one of three new wide releases to make it into the top ten. Three other wide openers, meanwhile, failed to live up to expectations.
Overall, the weekend's top ten films grossed just over $91m, nearly 44% up on the corresponding weekend last year.
Buena Vista opened Beverly Hills Chihuahua, about a pampered pooch that gets lost in Mexico, in 3,215 theatres and reaped a per-theatre average of $9,020.
Directed by Raja Gosnell and featuring voice performances from Drew Barrymore, Andy Garcia, George Lopez, Cheech Marin and others, the PG live-action comedy (with CG enhancements) was sniffed at by critics, but moviegoers, who have lately been starved of family fare, lapped it up.
The opening was bigger than those of most recent talking animal movies - 2001's Cats and Dogs, for example, started with $21.7m on the way to a $93m total - and beat all of Disney's previous dog tales with the exception of the 1996 live action 101 Dalmatians, which started with $33.5m and ended up with $136.2m.
Last week's number one, the DreamWorks-Paramount thriller Eagle Eye, was pushed into second spot, though it was down less than 40% with an estimated $17.7m from 3,516 theatres (average $5,034).
Sony's Nick and Norah's Infinite Playlist opened in third place with $12m from 2,421 theatres (average $4,957). The music-heavy comedy from Mandate Pictures has Peter Sollett directing Michael Cera and Kat Dennings as young New Yorkers on an eventful night out. Boosted by positive reviews and a PG-13 rating, it successfully tapped into a youthful audience.
Warner's Appaloosa - a well-received Western directed by Ed Harris, produced by Groundswell and starring Harris and Viggo Mortensen as two lawmen united in their effort to protect a town but at odds over a woman - went wide after two weeks in limited release and grossed $5m from 1,045 theatres (average $4,799) to rank fifth on the chart.
An American Carol, the debut release from Vivendi Entertainment, was the top ten's third new wide release, grossing an estimated $3.8m from 1,639 theatres (average $2,325).
The David Zucker-directed satire about a Michael Moore-style documentary filmmaker (played by Kevin Farley) transformed by visiting spirits, got mixed reviews and lacked star power but successfully exploited the interest in politics that surrounds the US presidential election.
That interest might also have helped Lionsgate's Religulous, the R-rated documentary about religion directed by Larry Charles and featuring comedian Bill Maher. With its $3.5m gross from 502 screens (average $6,972) the documentary unexpectedly sneaked into the top ten.
Less successful, however, were Universal's Flash of Genius, Miramax's Blindness and MGM's How to Lose Friends and Alienate People, each of which opened this weekend in more than 1,000 theatres.
With Greg Kinnear starring in the true story of the man who invented intermittent windshield wipers and fought the car industry for recognition, Spyglass production Flash of Genius grossed an estimated $2.3m and ended up just outside the top ten.
Blindness, the Fernando Meirelles drama with Julianne Moore, Mark Ruffalo, Danny Glover and Gael Garcia Bernal as victims of a plague that robs people of their sight, took $2m.
How to Lose Friends and Alienate People, based on British journalist Toby Young's book about his disastrous stint working at an upscale New York magazine, grossed $1.4m. The UK-produced comedy starring Simon Pegg did, however, open top this weekend in its home territory.
Next weekend's wide releases are: Warner's CIA thriller Body of Lies, with Ridley Scott directing Leonardo DiCaprio and Russell Crowe; Fox's family fantasy adventure City of Ember, starring Bill Murray and Tim Robbins and directed by Gil Kenan; Universal's American football drama The Express (which had sneak previews this weekend), directed by Gary Fleder and starring Dennis Quaid; and Screen Gems' horror thriller Quarantine, with Jennifer Carpenter and Jay Hernandez starring for director Erick Dowdle.
Estimated Top 10 North America Oct 3-5, 2008
Film (Dist)/Int'l dist/Est wkd gross/Est total to date
1 (-) Beverly Hills Chihuahua (Buena Vista) WDSMPI $29m -
2 (1) Eagle Eye (DreamWorks-Paramount) PPI $17.7m $54.6m
3 (-) Nick and Norah's Infinite Playlist (Sony) SPRI $12m -
4 (2) Nights In Rodanthe (Warner Bros) WBPI/Village Roadshow $7.4m $25m
5 (-) Appaloosa (Warner Bros) New Line Int'l $5m $5.6m
6 (3) Lakeview Terrace (Sony) SPRI $4.5m $32.1m
7 (5) Burn After Reading (Focus Features) FFI $4.1m $51.6m
8 (4) Fireproof (Samuel Goldwyn Films) $4.1m $12.5m
9 (-) An American Carol (Vivendi Entertainment) $3.8m -
10 (-) Religulous (Lionsgate) IM Global $3.5m -