||In this study, the port (inlet and outlet) and frictional pressure drops of a single-phase flow using liq- uid water and a two-phase flow using R1234ze(E) in a plate heat exchanger (PHE) are measured and analyzed by varying the flow direction, number of channels, temperature, mass flux, and vapor quality. The port-pressure drops are significantly dependent on the resistance of the flow through the channel guide in the PHE. In single-phase flow of liquid water, the port-pressure drop is proportional to the num- ber of channels and the Reynolds number, while the frictional pressure drop exhibits little dependence on the number of channels. Additionally, the port-pressure drop is affected by the flow direction owing to gravity. In two-phase flow of R1234ze(E), the port-pressure drops are significantly dependent on the flow direction owing to the distinctive non-uniformity of the two-phase flow distribution over the chan- nels. The existing correlation substantially underpredicts the measured port-pressure drops. Accordingly, new empirical correlations for the port-pressure drops are developed with high precision, in terms of the kinetic energy of the fluid, the Reynolds number, the normalized density ratio, and the number of channels.