The extraction of residual oil from palm pressed fibre (PPF) via aqueous enzymatic oil extraction (AEOE) process was studied based on the different operational variables. An application of the response surface methodology (RSM) and Box-Behnken Factorial Design by using a statistical package was used to develop a process design and modelling of the AEOE process. Ultrasonication was applied as a pre-treatment before the aqueous enzymatic oil extraction (AEOE) process, resulting in a both significant increase in yield and a reduction in process time. The use of Celluclast^® 1.5L FG in AEOE gave a 58.91% oil yield at pH 5.6 in 5 hr at 50°C. Incorporating the ultrasonication at 485 W for 15 min prior to the additional of Celluclast^® 1.5L FG increased the oil yield to 60.96% and reduced the extraction time to 3 hr. The effect of Celluclast® 1.5L FG on oil yields and glucose production from PPF combined with other processed parameters such as hydrolysis time, X₁, enzyme to fibre ratio, X₂ and liquid to fibre ratio, X₃ were also determined. The results of analysis of variance (ANOVA) indicated that in both models, oil extraction (Y₁) and glucose production (Y₂) were statistically significant (oil extraction, p<0.01 and glucose production, p<0.0001). Post-ANOVA showed that hydrolysis time, X₁ (p-value< 0.0001) and the enzyme to fibre ratio, X₂ (p-value 0.0038) had a significant (p<0.05) effect on the oil extraction, Y₁; whereas all the independent variables such as hydrolysis time, X₁ (p-value< 0.0001), enzyme to fibre ratio, X₂ (p-value 0.0002) and liquid fibre ratio, X₃ (p-value 0.0279) had a significant effect (p<0.05) on glucose production, Y₂. The observation confirms the results that the combination of the ultrasonication step as a pre-treatment and AEOE using Celluclast^® 1.5L FG increases the oil extractability at reduced time.