Environmental signals exert influences not only on the current generation, but also extend to subsequent generations, even when these signals no longer persist. These transgenerational effects can be mediated through several mechanisms, including epigenetic inheritance and composition of the gut microbiome. In this study, we investigated the contribution of the microbiome to diet-induced transgenerational effects on reproductive dormancy. Multiple strains of Drosophila simulans were subjected to a shift from a sugar-rich to a sugar-poor diet and the impact of this diet switch on dormancy was determined over multiple generations. Consistent with significant transgenerational effects, we observed a gradual reduction in dormancy incidence with an increasing number of generations exposed to the new, sugar-poor diet. Despite the variation in dormancy induced by the dietary shift, the microbiome composition remained largely stable. Consequently, we conclude that these transgenerational effects are not determined by changes in the bacterial microbiome composition.