Biodiesel has attracted a great deal attention recently as an alternative fuel due to increasing fuel prices and the imperative to reduce emissions. Among a wide range of biodiesel resources, microalgae are a promising alternative fuel source because of the high biomass, lipid productivity and environmentally friendliness. Microalgae is also a non-edible food, therefore, there will be no impact on the human food supply chain. In this work, petroleum diesel (PD) and biodiesel from the microalgae Chlorella protothecoides (MCP-B20) blend have been used to examine the performance and the emission of a 25.8 kW agriculture tractor engine. Two engine speeds at maximum power take off (PTO) power and torque have been selected for analysis using analysis of variance (ANOVA). The results showed that there is no significant difference between the engine performance when microalgae biodiesel blend (MCP-B20) and PD were used. However, a significant reduction in CO, CO2 and NO emissions was found when MCP-B20 was used. These outcomes give strong indication that microalgae can be successfully used in tractors as alternative fuel.