"Guardians" rang up $16.3 million in U.S. and Canadian ticket sales from Friday through Sunday, topping weekend charts for the third time since its Aug. 1 debut, according to estimates from tracking firm Rentrak. Total domestic sales climbed to $274.6 million, surpassing the $259.8 million earned by April release, "Captain America: The Winter Soldier."
Giant robot sequel "Transformers: Age of Extinction," which had a June 27 U.S. opening, reigns as the year's top-grossing film worldwide with more than $1 billion in sales, including a domestic haul of $244.3 million, according to boxofficemojo.
"Guardians" has earned $547.7 million around the globe, distributor Walt Disney Co said.
The big-budget space adventure stars Chris Pratt and Zoe Saldana as leaders of an oddball group of warriors that includes a talking raccoon and a humanoid tree.
In a sign of the film's staying power, Disney said ticket sales were down only 5 percent from last weekend. But the strength of "Guardians" is a bright spot in a sluggish summer for Hollywood at domestic theaters.
U.S. and Canadian ticket sales stood at $4.02 billion from the first weekend in May through Sunday, or 14.7 percent below last year, according to Rentrak's estimates. This year's films didn't keep pace with 2013's record-generating crop which included "Iron Man 3" and "Despicable Me 2."
Summer is the movie industry's biggest season, accounting for as much as 40 percent of the entire year's receipts.
"This summer was placed in the unfortunate position of being the follow-up to the biggest revenue generating summer of all time," said Paul Dergarabedian, senior media analyst at Rentrak, calling 2013 "a perfect storm" with franchises such as "Iron Man" and "Star Trek" becoming colossal hits.
"One or two movies can make all the difference," he added, noting that "Iron Man 3" alone injected $400 million last summer, while 2014 has yet to see any films break even the $300 million mark at the domestic box office.
For the weekend, "Teenage Mutant Ninja Turtles" took the No. 2 slot, collecting $11.8 million at North American (U.S. and Canadian) theaters through Sunday.
Drama "If I Stay," based on a young adult novel about a girl who has an out of body experience after a catastrophic car accident, claimed third place with $9.3 million.
Low-budget horror flick "As Above, So Below" debuted in fourth place, pulling in an estimated $8.3 million. The movie follows a team of explorers who venture through the catacombs beneath Paris. Legendary Pictures produced the film for $5 million.
New release "The November Man" finished sixth with $7.7 million, behind R-rated comedy "Let's Be Cops" with a $8.2 million take. "November Man" stars former James Bond actor Pierce Brosnan as an ex-CIA operative recruited for a mission that pits him against a former pupil.
"November Man" was distributed by privately held Relativity Media. Paramount Pictures, a unit of Viacom Inc, released "Transformers" and "Teenage Mutant Ninja Turtles." "If I Stay" was released by Warner Bros., a unit of Time Warner Inc.