Recent evidence in in vitro and in vivo models suggests that sulforaphane (SFN), found in raw cruciferous vegetables, may have utility in chemoprevention, as an antineoplastic agent and as a free radical scavenger. The effects of SFN alone or with doxorubicin on cell viability were examined, as well as cell cycle kinetics, invasion capabilities and apoptosis in three canine osteosarcoma cell line (D17, OS 2.4 and HMPOS). Results showed that SFN could not induce cell death at potentially physiological concentrations (<50 μM), but significantly diminished cell invasion and downregulation of focal adhesion kinase (FAK) signaling. Modest cell cycle changes were observed in each cell line. When doxorubicin was used in conjunction with SFN, there was a protective effect to doxorubicin-induced cytotoxicity in D17 and OS 2.4 cells. Further studies examining SFN as a supplement are warranted, particularly in light of pro-proliferative and cytoprotective properties in canine osteosarcoma.