Aluminium powder metallurgy (PM) is a near-net shape fabrication technology with a thriving market for various industrial niches. The basic sequence of manufacturing involved in the conventional PM process includes compaction, sintering, and secondary processing. It is known that most parts produced either through PM or other manufacturing technologies, depending on their engineering applications, are susceptible to fatigue cracking. Most notably, fatigue cracks often initiate from the surface of metallic components. Meanwhile, post-surface treatment processes such as shot and laser shock peening, which act to impose compressive surface stresses, are used to suppress and/or prevent the initiation of fatigue cracks for many metallic systems. While these surface modification technologies yield viable peening outcomes, there are operational costs and other drawbacks associated with them. For example, laser shock peening causes thermal damage to aluminium alloys and consequently affects the mechanical behaviour. It is envisaged that ultrasonic pulsed waterjet (UPWJ) peening, which offers a cleaner, safer, and more cost-effective approach compared to shot and laser shock peening counterparts, can be used as an alternate peening method to process aluminium alloys. Therefore, the objectives of this work are to assess the effects of UPWJ peening on the topographical, microstructural, and fatigue properties of an industrial PM aluminium alloy composite (with 5 wt.% AlN particles). The main finding from this work indicated gains in fatigue strength of up to 10% in the UPWJ peened aluminium alloy composite in comparison to the un-peened counterpart.