The objective of this study is to examine the influence of ultrasonic pulsed water jet (UPWJ) peening upon Ti-6Al-4 V (Grade 5), through evaluation of the microstructure, surface roughness, and residual stress development. The UPWJ peening treatment was conducted by varying the traverse speed, from 200 to 1000 mm/s, at a constant jet pressure of 69 MPa, frequency of 20 kHz, and stand-off distance of 25.4 mm. The average values of Ra, Rz, and Rsm roughness were recorded using laser confocal microscopy at each traverse speed. The residual stress distribution was analysed through sequential electropolishing of the unpeened and peened surfaces, followed by X-ray diffraction measurements. UPWJ peening resulted in only minor changes to the surface roughness when peening with traverse speeds in a range of 600 to 1000 mm/s. Surface residual compressive stresses for the peened Ti-6Al-4 V samples ranged between −628 ≤ σ ≤ −151 MPa, with the highest value obtained at a traverse speed of 800 mm/s. In-depth residual compressive stress of the treated region was also observed, up to a maximum depth of ~250–300 μm for traverse speeds between 400 and 1000 mm/s. Based on this study, the UPWJ method of surface treatment, where the efficiency of the water jet is enhanced through ultrasonic pulsing, has significant potential for the ‘green’ treatment aerospace and automotive engineering components.