A simple model predicting the effect of capillary flows on the condensation heat transfer occurring on a vertical grooved plate is presented. The model includes the effect of capillary flows along the axial direction of the grooves and the direction from the apex to the cornered region of the groove. Numerical results indicated that the capillary flow induced by the capillary force significantly affects the condensation heat transfer, as does the plate height, groove width, and groove angle. In order to verify the theoretical prediction, an experimental investigation was conducted, and the theoretical prediction agrees well with the experimental data. Results of the investigation will assist in optimizing the condensation heat transfer performance in heat pipes.