A ten week old Border Collie mix presented with recurrent lethargy, inappetence, and vomiting. In the two weeks prior to presentation, sulfadimethoxine, abendazole, and fenbendazole treatments were administered for parasitism and suspected infection. Results of a complete blood count on presentation revealed pancytopenia. Cytological evaluation of a bone marrow aspirate showed hypercellularity and regenerative changes. Fluid therapy, antibiotics, and discontinuation of the other medications resulted in a complete recovery. Drug-induced bone marrow suppression was suspected based on resolution of pancytopenia following drug withdrawal and absence of infectious, neoplastic, autoimmune, and primary bone marrow disease.