Urolithiasis has been reported in veterinary literature in some species of the Mustelidae family, including ferrets. In this species, the most common form of urolithiasis is that caused by struvite. The current study examined the case of mixed urolith in an 8-month-old female ferret ( Mustela putorius furo) with antecedents of strangury and hematuria. A cystotomy was carried out to remove the urolith, which had a rough surface and a homogeneously porous interior and was formed by a mixture of struvite (60%) and calcium oxalate dehydrated (40%).