The objetive of this study was to compare a single dose of secnidazole versus multiple doses of fenbendazole for the treatment of dogs with asymptomatic Giardia infection. Materials and methods: Twenty-four asymptomatic dogs with a positive test result for Giardia spp were randomized in two equal groups to receive a single dose of secnidazole at 30 mg/kg PO, or fenbendazole at 50 mg/ kg PO q24h for 3 days. Hematological parameters were evaluated before and 8 days after treatment, and feces were re-examined at days 8, 15, and 30 post-treatment by fecal flotation and antigen test. Results: The number of positive dogs in the fenbendazole group was: 1 (day 8) and 3 (days 15 and 30). In the secnidazole group, the number of positive cases were: 4 (day 8), 3 (day 15), and 1 (day 30). Conclusion: Treatment with secnidazole or fenbendazole, were effective between 75% and 92% to eliminate the excretion of Giardia cysts in canines together with hygienic measures to control, like disinfection with quaternary ammonium of patients and their environment. Further studies that include more animals and multiple fecal exams on consecutive days would be necessary to confirm its efficacy in dogs.