Ten fungal isolates with an ability to degrade crude oil were isolated from select marine substrates, such as mangrove sediments, Arabian Sea sediments, and tarballs. Out of the ten isolates, six belonged to Aspergillus, two to Fusarium and one each to Penicillium and Acremonium as identified using ITS rDNA sequencing. The selected ten fungal isolates were found to degrade the long-chain n-alkanes as opposed to short-chain n-alkanes from the crude oil. Mangrove fungus #NIOSN-M126 ( Penicillium citrinum) was found to be highly efficient in biodegradation of crude oil, reducing the total crude oil content by 77% and the individual n-alkane fraction by an average of 95.37%, indicating it to be a potential candidate for the development into a bioremediation agent.