The present study was intended to determine the cytotoxic and apoptotic effects, which occurred due to the fact that ellagic acid and etoposide combinations were administered dose and time dependently, on D-17 canine osteosarcoma cells. The effect of etoposide and ellagic acid administered to D-17 canine osteosarcoma cell line on cell viability and the IC50 value were determined with the WST-1 viability test for incubation times of 24, 48 and 72 hours (IC50 value of ellagic acid was 30.72 μM for 48 hours, 16.91 μM for 72 hours and IC50 dose of etoposide was 19.3 μM, 13 μM and 11.36 μM for 24, 48 and 72 hours, respectively). In line with the IC50 values; by combining ellagic acid and etoposide concentrations at different rates, their cytotoxic effects were researched in the 24-, 48- and 72-hour cell culture incubations. Combination index values of the mentioned concentrations were calculated as CI<1 using the CompuSyn program. The combination doses exhibiting synergistic action were used for 24- and 48-hour incubation times for apoptotic analyses. In cells to which the determined combinations were administered; the effect of combination on metastasis was determined doing invasion and migration analyses. The apoptotic effects of the administered combination on the cell were indicated analyzing the DNA fractures with the electrophoretic and ELISA methods. The effect of combination on caspase-cascade system in the apoptotic pathways was detected by determining the Caspase 3, Caspase 8 and Caspase 9 activities with ELISA method. The effectiveness of combination in taking cells to apoptosis was researched by determining the rates of viable, apoptotic/necrotic cells with Acridine Orange/Ethidium Bromide staining method. Moreover, expression levels of survivin and NF-κB genes, regarded as genes related to proliferation and survival of Bcl-2, Bax and Bid genes and cells in the apoptotic pathways, were determined using RT-PCR methods. The results of the study found out that administration of ellagic acid alone in D-17 canine osteosarcoma cells exhibited an anti-cancer effect in vitro. Using it in combination with etoposide exhibited a synergistic effect and an anti-cancer effect was obtained, which was higher than the apoptotic rate which etoposide exhibited alone. In this respect, it is considered that ellagic acid can be a potential drug candidate which may be supportive of chemotherapy but the scope of studies on this subject should be broadened and their accuracy should be proven with further molecular studies and by trying them on in-vivo animal models.