Petroleum diesel is a conventional energy source that powers various means of transport, generally to power internal combustion engines/compression ignition engine. The processes of extraction, refining, transport and storage of petroleum are prone to leaking and spilling accidents, resulting in environmental contamination. Due to environmental concern, researches community search for the some significant technologies to reduce environmental contamination by blending of biodegradable biodiesel fuel with diesel. The biodegradability of biodiesel is the strongest point in the case for their use as an alternative fuel for diesel engine. Awareness of the biodegradability of substance is one of the most important features of their environmental aspects because a biodegradable substance is expected to cause less ecological problems in the long term than a persistent one. On the basis of the literature review, it is found that the rate of degradation of petroleum diesel will be increased with the biodiesel concentration which will increase in the blends. Hence, this article gives an overview of biodegradable behaviour of biodiesel and its diesel blends.