The role of plasmid-borne genes in the biodegradation of Chevron Escravos Crude Oil by bacteria was determined. Plasmid extraction and curing, transformation experiments and biodegradation studies were carried out using standard procedures. Plasmid extraction studies showed that two of the six selected crude oil degrading bacterial isolates had two plasmids each. The isolates were Klebsiellaaerogenesfrom ripe pawpaw fruit and Serratiamarscescens from oil palm mill effluent. The plasmids were of small (300bp) and large (>1.5kbp) sizes. The results also showed that the isolates were successfully cured of plasmids using 1% Sodium Dodecyl Sulphate (SDS). The transformation experiment using the extracted plasmid DNA and competent Escherichia coli K12 DH1 cells was successful. The percentage degradation of crude oil at 37oC by E. coli K12 DH1 transformed with the plasmid DNA from Klebsiellaaerogeneswas 93.03%while that transformed with the plasmid DNA fromSerratiamarscescens degraded 76.97% of the crude oil. It was observed that loss of plasmids byKlebsiellaaerogenesand Serratiamarscescens did not lead to complete loss of their degradative abilities. It only resulted in reduction in their degradation potential. These findings showed that plasmid encoded genes play a role in crude oil degrading capability of bacterial isolates.