Biotreatment of methylparathion was studied in aqueous mineral salts medium containing bacterial culture to demonstrate the potential of the novel strain of Pseudomonas aeruginosa mpd. A statistical Box–Behnken Design (BBD) of experiments was performed to evaluate the effects of individual operating variables and their interactions on the methylparathion removal with initial concentration of 1000 mg l-1 as fixed input parameter. The temperature (X1), pH (X2), reaction time (X3) and agitation (X4) were used as design factors. The result was shown that experimental data fitted with the polynomial model. Analysis of variance showed a high coefficient of determination value 0.9. The optimum biodegradation of MP in terms MP removal (Y1), COD removal (Y2) and TOC removal (Y3) were found to be 95.2 %, 82 % and 61.2 % respectively. The maximum growth (Y4) was 2.18 optical density (OD). The optimum biodegradation correspond to the factors combination of middle level of X1 (33 oC), X2 (7.0), X4 (150 rpm) and the highest level of X3 (96h). MP removal and its residues were detected using spectral analysis. The study demonstrates the optimum MP biodegradation potential of this strain could use MP as the sole Carbon/Phosphate source. BBD confirmed to be dependable in developing the model, optimizing factors and analyzing interaction effects. Data from this study will be helpful in the design of small-scale field experiments and subsequently an in situ methylparathion biotreatment system for field application.