Retail giant accused of knowingly selling adulterated tequila containing “significant presence of non-agave sugars”

Costco is in the crosshairs of a new class-action lawsuit filed by Seattle-based consumer-rights law firm Hagens Berman, accusing the retailer of knowingly selling adulterated tequila that contains “significant presence of non-agave sugars.”

The lawsuit was filed Nov. 14, 2025, in the U.S. District Court for the Western District of Washington and states that despite Costco labeling its Kirkland Signature tequila as “100% DE AGAVE” and as “100% AGAVE AZUL,” attorneys have uncovered evidence, including scientific testing, that it is adulterated, and not pure agave as marketed. Affected products include Costco Kirkland Blanco Tequila, Reposado Tequila, Añejo Tequila, Añejo Cristalino Tequila and Extra Tequila Añejo products.

If you purchased Costco’s Kirkland tequila in the U.S., you may be affected. Find out your consumer rights.

“We believe Costco’s marketing of its tequila products is two-faced, and that despite marketing it as a premium – and reflecting that in its price – consumers have been misled about the quality of Kirkland Signature,” said Steve Berman, managing partner and co-founder of Hagens Berman. “Consumers who purchased Kirkland tequila didn’t get what they paid for, plain and simple.”

The law has also filed a class-action lawsuit regarding similar claims against Diageo, global conglomerate and maker of Casamigos and Don Julio brand tequila.

“High-Stakes Deception” in a Popular Market

The lawsuit filed against Costco details the circumstances surrounding the market of premium tequila, accusing the retailer of “seeking to capitalize on consumer demand for authentic, high-quality tequila” in its marketing. According to the lawsuit, consumers pay a premium price for spirits made from 100% Blue Weber agave because of the crop’s long growing season and difficulty of harvesting.

Reports cited in the lawsuit state premium tequila sales have grown 1,270% since 2003, with super-premium brands up 1,500% over the same period.

The definition of tequila is strictly regulated in the U.S. and Mexico, according to the lawsuit, with standards set for production, labeling and marketing: “To prevent adulteration, the Tequila NOM [the official Mexican standard] imposes strict documentation requirements.” To qualify as “100% agave,” a tequila’s “fermentation may not be enhanced with sugars other than those obtained from the tequilana weber blue variety Agave.”

According to the lawsuit, the Tequila NOM imposes strict documentation requirements to prevent adulteration, including maintaining records, invoice and documents confirming raw materials, movement of finished materials and inventories.

“But scientific testing using established and accepted testing methodologies, including nuclear magnetic resonance (NMR) and isotope testing, reveals the significant presence of non-agave sugars in Kirkland Tequila Products,” the lawsuit states. “These findings contradict Costco’s ‘100% de Agave’ or ‘100% Blue Agave,’ representations and confirm its tequilas are adulterated.”

A Tequila Cartel

According to the firm, Costco’s consumer deception amounts to violations of the Racketeer Influenced and Corrupt Organizations (RICO) Act, a law pertaining to organized criminal behavior. The lawsuit also brings claims of violation of state consumer protection laws pertaining to unfair competition, unfair trade practices and fraudulent concealment.

The lawsuit reveals that the organization that has taken charge of ensuring compliance with the Tequila NOM is the Consejo Regulador Del Tequila A.C. (CRT).

“Although CRT presents itself as a regulatory body, it is not a governmental entity. Rather, it is a private non-profit organization composed of members from across the Agave-Tequila production chain… Notably, CRT’s Board of Directors and committees are dominated by representatives of well-known tequila producers,” the lawsuit states. “In effect, the very companies that CRT purports to regulate are the ones running it.”

Attorneys representing consumers in the lawsuit seek to put an end to Costco’s allegedly deceptive behavior and to recover losses paid by consumers for the affected Kirkland Signature tequila.

Read more about the lawsuit filed against Costco for allegedly adulterated tequila.

About Hagens Berman

Hagens Berman is a global plaintiffs’ rights complex litigation law firm with a tenacious drive for achieving real results for those harmed by corporate negligence and fraud. Since its founding in 1993, the firm’s determination has earned it numerous national accolades, awards and titles of “Most Feared Plaintiff’s Firm,” MVPs and Trailblazers of class-action law. More about the law firm and its successes can be found at hbsslaw.com. Follow the firm for updates and news at @ClassActionLaw.

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“We believe Costco’s marketing of its tequila products is two-faced, and that despite marketing it as a premium – and reflecting that in its price – consumers have been misled about the quality of Kirkland Signature,” said Steve Berman.