Abstract: Understanding the axial pressure drop and transverse pressure distribution on the cross-section of wire-wrapped rod bundle assemblies is essential for thermal-hydraulic design and gaining deeper insights into flow-induced vibrations within the assembly. However, there is a scarcity of experiments conducted at low velocities, and the number of experimental studies on the transverse pressure distribution is limited to only two. In this study, an experimental investigation on axial pressure drop and transverse pressure distribution at two cross-sections was conducted over a range of flow rates, from 0.066 7 to 1.561 m³/h, corresponding to Reynolds numbers in the range of 55 to 1 290. An improved liquid column manometers using digital image technology and a mass flow rate measurement approach were employed to enhance the measurement accuracy of the pressure difference and volume flow rate. Experimental results show that, during the transition from laminar to transitional flow within the localized flow region of the assembly, the Reynolds number must increase from 250 to 750 before a significant deviation from the laminar friction factor correlation is observed. The pressure distribution across the edge subchannels at the cross-section is nearly symmetric around the radial line at 120° from the wire. The region between 90° and 120° from the wire on the cross-section of the assembly is the area of maximum pressure, while the region between −60° and −90° behind the wire corresponds to the minimum pressure area. By nondimensionalizing the relative pressure values of the edge subchannels using the dynamic pressure of the water flow inside the assembly, the nondimensional relative pressure for different edge subchannels was obtained. Regardless of whether the wire is aligned with the box wall of the assembly or with the angle between the two box walls, as the Reynolds number increases, the nondimensional relative pressure of the different edge subchannels gradually converges to a constant value. The study indicates that the transition from laminar to transitional flow in the wire-wrapped rod bundle assembly occurs over a wide range of Reynolds numbers. The error in the critical Reynolds number determination using the visual inspection method of frictional resistance pressure drop and friction factor is relatively large. Furthermore, the pressure differences among the edge subchannels are found to be proportional to the dynamic pressure of the transverse flow velocity between the subchannels.