Mycolicibacterium fortuitum is a fast-growing bacterium and an opportunistic pathogen implicated in human and animal infections. Here we report the first case and genetic characterization of a strain of M. fortuitum isolated from skin lesions of a companion cat with atypical cutaneous mycobacteriosis in Brazil. In addition, the genome of this strain was sequenced, representing the first genome of this opportunistic pathogen isolated from an animal infection. The in silico and in vitro analysis regarding antibiotic resistance of this strain showed an intrinsic multiresistance antibiotic profile. However, this strain showed sensitivity to amikacin and ciprofloxacin, and the cat was treated long-term with these drugs.