Microchannel (MC) emulsification is a novel technique for producing monodisperse emulsions. We previously proposed a droplet diameter prediction model for simple MC structures consisting of a narrow channel and a slitlike terrace. In this study, the prediction model is expanded to MCs with partition walls. The geometry of an MC with a partition wall is defined by five parameters: channel length, channel width, terrace length, terrace width, and MC depth. The droplet diameter prediction models are proposed under the simple assumption that the portion of the dispersed phase within the detachment length from the terrace end detaches and forms a discrete droplet. The volumes of the detaching dispersed-phase droplets are calculated, and the calculated values are compared with the experimental data. The mean percentage deviation of the calculated values from the experimental results is 5.7%, and all of the data have deviations within 11%.