Joining forces with the Humane Society of the United States, the Crazy, Stupid, Love actor is taking a stand against the retail giant for selling eggs produced by caged chickens.
"I am writing today about the recent undercover investigation conducted by my friends at The Humane Society of the United States at a Costco egg supplier," Gosling began his letter on Monday. "Video footage revealed abhorrent cruelty including rows upon rows of birds confined in filth-laden cages with the mummified corpses of their cage-mates—eating, sleeping, defecating, and laying eggs on top of dead birds—and hens' wings, legs, and necks trapped in the corroded wires of their battery cages."
Ryan Gosling in recent years
Ryan Gosling stands up for chickens in letter to Costco
Director Ryan Gosling poses during a photo call for Lost River at the 67th international film festival, Cannes, southern France, Tuesday, May 20, 2014. (AP Photo/Alastair Grant)
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Canadian actor Ryan Gosling poses as he arrives for the screening of the film 'Lost River' at the 67th edition of the Cannes Film Festival in Cannes, southern France, on May 20, 2014. AFP PHOTO / VALERY HACHE (Photo credit should read VALERY HACHE/AFP/Getty Images)
From left, actor Josh Brolin, actress Emma Stone, and actor Ryan Gosling from the cast of "Gangster Squad," pose for a portrait at the Four Seasons Hotel on Saturday, Dec. 15, 2012, in Beverly Hills, Calif. (Photo by John Shearer/Invision/AP)
NEW YORK, NY - APRIL 11: Director Ryan Gosling attends Apple Store Soho Presents Meet The Filmmaker: Ryan Gosling, 'Lost River' at Apple Store Soho on April 11, 2015 in New York City. (Photo by Brad Barket/Getty Images)
Russell Crowe, Jack Kilmer and Ryan Gosling are seen on the set of 'The Nice Guys' on January 22, 2015 in Los Angeles, California. (Photo by TSM/Bauer-Griffin/GC Images)
AUSTIN, TX - MARCH 14: Director/writer Ryan Gosling takes part in a Q&A following the 'Lost River' premiere during the 2015 SXSW Music, Film + Interactive Festival at Topfer Theatre at ZACH on March 14, 2015 in Austin, Texas. (Photo by Michael Loccisano/Getty Images for SXSW)
AUSTIN, TX - MARCH 13: Actor/director Ryan Gosling (L) and director Guillermo del Toro partake in 'A Conversation With Ryan Gosling' during 2015 SXSW Music, Film + Interactive Festival at Austin Convention Center on March 13, 2015 in Austin, Texas. (Photo by Michael Loccisano/Getty Images for SXSW)
Actor Ryan Gosling attends the premiere of Focus Features' "The Place Beyond The Pines" at the Landmark Sunshine Theater on Thursday March 28, 2013 in New York. (Photo: Evan Agostini/Invision/AP)
Ryan Gosling and Donna Gosling attend the LA premiere of "Gangster Squad" at Grauman's Chinese Theater on Monday, Jan. 7, 2013, in Los Angeles. (Photo by John Shearer/Invision/AP)
THE PLACE BEYOND THE PINES 2012 Focus Features film with Ryan Gosling and Eva Mendes (Photo via Alamy)
Director, writer, and cast member George Clooney, right, and cast member Ryan Gosling pose together at the premiere of "The Ides of March", in Beverly Hills, Calif., Tuesday, Sept. 27, 2011. "The Ides of March" opens in theaters Oct. 7, 2011. (AP Photo/Matt Sayles)
NEW YORK, NY - JULY 20: Ryan Gosling along with his dog George visits 'Late Night With Jimmy Fallon' at Rockefeller Center on July 20, 2011 in New York City. (Photo by Theo Wargo/Getty Images)
Ryan Gosling and Emma Stone arrive at the "Crazy Stupid Love" premiere in New York, Tuesday, July 19, 2011. (AP Photo/Charles Sykes)
Steve Carell, left, and Ryan Gosling arrive at the "Crazy Stupid Love" premiere in New York, Tuesday, July 19, 2011. (AP Photo/Charles Sykes)
TORONTO, ON - SEPTEMBER 07: Actors Eva Mendes and Ryan Gosling attend 'The Place Beyond The Pines' premiere during the 2012 Toronto International Film Festival at Princess of Wales Theatre on September 7, 2012 in Toronto, Canada. (Photo by Sonia Recchia/Getty Images)
CANNES, FRANCE - MAY 20: (L-R) Actors Reda Kateb, Ryan Gosling, Christina Hendricks and Geoffrey Arend attend the 'Lost River' premiere during the 67th Annual Cannes Film Festival on May 20, 2014 in Cannes, France. (Photo by Foc Kan/FilmMagic)
This March 10, 2013 photo shows Canadian actor Ryan Gosling poses for a portrait in New York. Gosling plays a tattooed motorbike rider in a traveling circus in his latest film,"The Place Beyond the Pines." (Photo by Victoria Will/Invision/AP)
Danish director Nicolas Winding Refn (R) is congratulated by actor Ryan Gosling during a photocall after being awarded with the Prix de la Mise en Scene (best director) for his film 'Drive' at the 64th Cannes Film Festival on May 22, 2011 in Cannes. AFP PHOTO / ANNE-CHRISTINE POUJOULAT (Photo credit should read ANNE-CHRISTINE POUJOULAT/AFP/Getty Images)
After he describes the video footage, he then claims that Costco has been deceiving people about their eggs.
"Furthermore, it is appalling that Costco has been selling these eggs with deceptive labeling on cartons featuring graphics of birds living out in a green pasture," he wrote. "You're already eliminating cages for veal calves and pigs – don't you feel that chickens also deserve the same mercy?"
Gosling is hopeful that Costco will go completely cage-free with its eggs.