We investigated the cytotoxic effects of the newly synthesized cyclotriphosphazene derivatives on A2780 (ovarian), PC-3 and LNCaP (prostate) cancer cell lines. 4'-hydroxy-substituted-chalcone compounds (2-8) were reacted with diphenyl-cyclotriphosphazene (DPP) in the presence of acetone/K2CO3 in order to obtain novel cyclotriphosphazene compounds (DPP 2-8). The structures of DPP2-8 were characterized by MALDI-TOF mass spectrometry, FT-IR, elemental analysis, H-1, C-13-APT, and P-31 NMR measurements. The thermal properties of all phosphazene compounds have been studied after synthesis and characterization procedure. The cytotoxic effects of DPP 2-8 were examined primarily by applying the MTT method based on the measurement of mitochondrial activity. In this regard, several phosphazene compounds have shown high chemotherapeutic effect at low dose (p < 0.05). When the cytotoxic effects of DPP 2-8 at doses of 1, 5, 25, 50 and 100 mu M on A2780 cells were examined, it was observed that DPP-3, DPP-4, DPP-5 and DPP-7 were more effective than other derivatives suggested by their high Log IC50 values (p < 0.05). The compounds DPP 2-8 possess cytotoxic activity against PC-3 and LNCaP cells (especially compounds DPP-4 and DPP-5, p < 0.05).