Animals are naturally surrounded by a variety of microorganisms with which they constantly interact. Among these microbes, some live closely associated with a host and form its microbiota. These communities are now extensively studied, owing to their contributions to shaping various aspects of animal physiology. One of these commensal species, Lactobacillus plantarum, and in particular the L.p.WJL strain, has been shown to promote the growth of Drosophila larvae upon nutrient scarcity, allowing earlier metamorphosis and adult emergence compared to axenic individuals. As for many insects, conditions surrounding the post-embryonic development dictate key Drosophila adult life history traits, and adjusting developmental timing according to the environment is essential for adult fitness. The growth acceleration induced by L.p.WJL occurs in a context of poor nutrition and we wondered if this could adversely impact the fitness of Drosophila adults. Here we show that the L.p.WJL-mediated acceleration of growth is not deleterious; adults emerging after an accelerated development are as fit as their axenic siblings. Additionally, L.p.WJL presence even leads to a lifespan extension in nutritionally challenged males. These results demonstrate that L.p.WJL is a beneficial partner for Drosophila melanogaster through its entire life cycle. This commensal bacteria allows the earlier emergence and longer survival of fit and fertile individuals and might represent one of the factors contributing to the ecological success of Drosophila.