New modifications are added to the serpentine flow field to enhance the performance of direct methanol fuel cell. The modifications are based on increasing the pressure difference between adjacent channels to increase the under-rib flow. The width of flow channel is contracted between parallel channels with different width values of 0.8, 0.6, and 0.4 mm. The height of the flow field is also decreased from 0.8 to 0.4 mm. To determine the performance parameters of newly proposed designs, a three-dimensional single-phase isothermal model is developed, numerically simulated, and validated using experimental measurements. Decreasing contraction width from 0.8 to 0.4 mm achieved an increase in net generated power density by 6% compared with conventional non-contracted configuration. The maximum increase in performance was 25% and it was noticed when decreasing flow field height to 0.4 mm and using contraction width of 0.4 mm. The increase in performance was a result of boosting reactants concentration by enhancing under-rib flow.