Two naturally occurring fungal and bacterial species, Aspergillus flavus and Bacillus sp. H6 strains, were capable of utilizing diesel oil as a sole source of carbon in synthetic microcosoms. The initial diesel oil contamination of 1666 mg kg^-1 dry soil was reduced to 166.667 mg kg^-1 after 150 days of incubation in fungal-bacterial consortium microcosm. That is mean 89.9%, of the initial oil concentration was removed. Abiotic process reduced the diesel oil contamination to about 616 mg kg^-1dry soil at the end of the experiment. Seven microcosms were set up to fulfill the experiments. The decontamination activity follow this order; Bacillus sp. H6 + A. flavus consortium > Bacillus sp. H6 > natural control > A. flavus > cycloheximide treated > benzyl Penicillin-Streptomycin treated > poisoned control. Gas chromatographic analysis data revealed that both A. flavus and Bacillus sp. H6 treatment led to complete utilization of carbon-17 compounds. Other biodegradation products such as C-15, 16, 20, 21, and 24 appears in the chromatogram after 150 days incubation. Increase of C-20, 21 and C-24 compounds also noticed. The fungal- and bacterium consortium treatment depicted a decrease of all detected n-alkanes. The microbial success in biodegradation was evaluated by determining the number of germinating seeds of Phaseolus vulgaris. The highest level of germination (92 %) was detected in consortium microcosms after 150 days incubation. The treatment with A. flavus and Bacillus sp. H6 separately led to a lower percentage of germination (86%). The other treatments showed variable results except the poisoned control that showed negative germination and minor chemical degradation of diesel oil. Thus, bacterial-fungal consortium treatment is effective in bioremediation of contaminated oils than separate treatment.