Onchocerciasis represents a filarial nematode parasitic infection of the ocular and periocular tissues, which may affect dogs. This chapter describes the infection in dogs with <i>Onchocerca lupi </i>and Onchocerca lienalis. This parasite cycles through a definitive wild host, adults mating to produce microfilariae, which may be vectored by either Simulium sp or Culicoides sp flies. Clinically, onchocerciasis may present as any combination of ocular discharge, blepharospasm, conjunctivitis, chemosis, episclerokeratitis, uveitis, and/or parasite‐containing granulomas affecting the episcleral or periocular tissues. The diagnosis of onchocerciasis is made on the basis of the identification of parasites and/or biopsy specimens. Treatment comprises surgical removal of granulomas, systemic anti‐inflammatory therapy, systemic antimicrobial therapy to destroy endosymbiotic Wolbachia sp, adulticide therapy and microfilaricide therapy.