The invasive fruit fly Drosophila suzukii is a highly successful pest worldwide. The use of mature fruits, a niche neglected by other drosophilids, and its polyphagy may have contributed to its global spread. Yet, polyphagy exposes the fly to substrates varying in nutritional quality and some are less favorable than others for larval development. Some insects may rely on symbiotic bacteria (e.g., Wolbachia) to better perform on a priori unfavorable substrates. The role of D. suzukii’s Wolbachia strain (wSuz) is still unknown but its mutualistic role to deal with abiotic stress has been hypothesized. Indeed, in few insect species, Wolbachia was found to be a nutritional mutualist. The aim of this study was to explore the wSuz role in D. suzukii adaptation to fluctuating diet regimes. To simulate a substrate shift, we used Wolbachia infected and uninfected flies that were maintained on a corn-based medium (poor quality diet) or a grape-based medium (rich diet) for at least 10 generations. Then, we placed individuals from each line on either one or the other media during 30 days. The effect of Wolbachia together with diet treatments was assessed on female fecundity, egg-to-adult development time, mortality, and offspring weight. The diet shift affected female fecundity and offspring weight: females coming from a corn medium laid more eggs on grape medium and the offspring weights were superior. Wolbachia reduced mortality during larval development regardless of the diet, supporting its mutualistic role. It also influenced offspring weight in interaction with the new diet. Our results contribute to a better understanding of wSuz and underline its role on diet tolerance. A better understanding of the role of symbionts in invasive species could lead to better management strategies.