Abstract The direct methanol fuel cell (DMFC) has a significant potential in consumer electronics and in backup and portable power. Its progress is, however, hindered, in part, by a lack of an adequate fundamental understanding of the effect of various operating and design variables on its performance. While detailed computational models are available, an analytical model is attractive for ease of comprehension and ready utility. Therefore, we have developed a comprehensive yet tractable one-dimensional, isothermal, explicit analytical model based largely on a priori parameters, and in terms of quantities with tangible meaning. The model correctly predicts the extent of methanol crossover and its effect on open-circuit voltage (OCV) as well as on polarization of the anode, cathode, and the fuel cell. It also accurately describes the effects of methanol feed concentration and temperature on DMFC performance. It aptly predicts the significant power losses from the large anode and cathode overpotentials as well as from methanol crossover, and the resulting low DMFC efficiency, except over a narrow range of operating conditions. The insightful model can be used, e.g., in real-time control of DMFC to operate in the narrow region of high efficiency and power density.