Demand for energy has increased as a result of population expansion and industrialization. Rapid utilization of petroleum diesel products leads to depletion of petroleum products. Emissions from diesel engines indeed have a significant influence on the environment, impacting both air quality and climate change. To overcome above problems, focus toward the alternative sources. Biodiesel is one of the alternative fuels extracted from animal fats, vegetable oils, and algae. Cashew nut shell methyl ester and Jack fruit methyl ester are tested in diesel engine with various piston shapes, including hemispherical, toroidal and double wedge. Testing on a single-cylinder diesel engine provides valuable insights into engine behavior and performance, aiding in the development of cleaner, more efficient, and more reliable diesel engines for various applications, including automotive, industrial, and power generation. According to the test findings, brake thermal efficiency is enhanced while specific fuel consumption is decreased. That carbon monoxide (CO) and hydrocarbon (HC) emissions are reduced while nitrogen oxides (NOx) levels are increased compared to diesel at full load suggests a complex factor affecting combustion within the engine.