Unreinforced masonry structures, especially prevalent in the historic centres of small and medium-sized towns in Italy and across Europe, are often vulnerable to both in-plane and out-of-plane failure mechanisms due to seismic actions. Specifically, damage from in-plane failure mechanisms is frequently intensified by soil-related phenomena. Among these, the most critical factors include differential settlements, groundwater depletion, mining operations, and the collapse of natural voids. The occurrence of soil settlements can result in additional damage to buildings and may significantly reduce their seismic capacity. Therefore, it is essential to consider the effects of soil settlements on the seismic performance of masonry structures. In this framework, this paper aims to explore how soil settlements influence the behaviour of masonry walls during seismic events. To achieve this, pushover analyses of representative masonry façades are conducted, considering various settlement profiles. Finally, a comparison in terms of capacity curves is carried out with the aim of assessing the reduction in seismic resistance of walls previously subjected to settlement compared to the reference condition subjected only to seismic action. Numerical analyses show that pre-existing damage due to foundation settlements always leads to a reduction in load-bearing capacity, even under seismic conditions. However, the extent of this reduction varies depending on the structural configuration and the area affected by the settlement, as illustrated in this paper.