The paper reported on the characterization of CTS oil-based biodiesel-diesel blends. The study's primary objective are the physicochemical characterization of oil and biodiesel from Cassia Tora seed (CTS) oil, characterization of CTS oil-based biodiesel using FTIR and GCMS analysis. Extraction revealed the pres-ence of 8.8% oil in Cassia Tora seed. The CTS biodiesel's viscosity was found to be 0.9092, which is well above the petroleum diesel. The physiochemical characterization showed that 5, 12.5 and 20 % CTS oil-based biodiesel-diesel blends are within acceptable limit for combustion engine without modification having viscosities of 0.8744, 0.8764, and 0.8787 respec-tively while 100% CTS oil-based biodiesel would require upgrading to meet up with the recommended standard for fuel used as diesel in internal combustion engines. FTIR and GCMS analysis showed functional groups and characteristic peaks of fatty acids and methyl ester with carbon range from C13–C17, C16 constituted the major Fatty acid group and contained 61.69 % Monounsaturated Fatty Acid (MUFA), and 38.31 % Saturated Fatty Acid (SFA) giving a 94.3% biodiesel yield.