Lululemon Athletica claims in its lawsuit filed in the U.S. District Court for the Central District of California that Costco has “unlawfully traded” on its reputation, goodwill and sweat equity by selling unauthorized and unlicensed apparel that uses knockoff, infringing versions of its patents.

Cheaper look-alikes have been around for years, but social media has made them more popular. Dupes can move into shaky legal territory if concerns arise around consumer confusion or patented designs.

Renowned apparel brand Lululemon has reportedly sued the popular membership-based warehouse club Costco. According to a People report, Lululemon filed a lawsuit in federal court in California on June 27, 2025. The legal dispute stems from Lululemon’s claim that Costco sold imitations of its signature apparel under the Kirkland brand.