Biodiesel is one of the renewable alternatives to the use of diesel of fossil origin, and its usage has been growing in the world. The production of biodiesel can be performed from a large variety of raw materials. Within these raw materials, a known highlight is the cottonseed, from which the oil can represent 20% of its mass. For this, this work has the goal to study, with an experimental and methodic approach, the behavior of an internal combustion engine when working with biodiesel produced from cottonseed and different blends of this biofuel with commercial diesel. The tested proportions were 100%, 80%, 50%, 20% and 0% of biodiesel in the blend. To make this research, the specific fuel consumption and the power generated on a diesel cycle conventional engine working at maximum power speed and plain load were observed. After the tests, it was identified that for every tested blend, the engine was able to develop a stable combustion and that as the percentage of biodiesel in the blend increased, there was a tendency of the fuel consumption increase and the reduction of the power generated by the engine, which did not overcome 9%.