Purpose <p>Soil microbial communities regulate key ecosystem functions, from nutrient cycling to organic matter decomposition. Yet, we lack a basic understanding of how microbial predators, such as collembola, influence these functions via microbial mediation. This study aims to investigate how collembola (<i>Folsomia candida</i>) influence soil microbial communities and associated ecosystem functions in a grassland context.</p> Materials and methods <p>We conducted a microcosm experiment simulating grassland vegetation, including high and low microbial diversity with and without the collembola <i>F. candida</i>. We measured microbial community composition, enzyme activities, nutrient cycling, and plant biomass to evaluate collembola effects on soil function.</p> Results and discussion <p>Collembola influenced microbial community composition, likely through feeding preferences, which in turn affected nutrient cycling and function. Soil microbial diversity promoted nutrient cycling, and <i>F. candida</i> inoculation supported even stronger positive effects on nutrient cycling and plant biomass. The effects of collembola on soil function were indirectly driven via changes in microbial taxa, leading to greater N-acetylglucosaminidase activity and nutrient cycling potential.</p> Conclusions <p>Our results demonstrate that springtail-mediated top-down effects can significantly alter carbon and nitrogen cycling by regulating microbial community composition in controlled microcosms. These findings highlight the necessity of incorporating trophic interactions and their underlying mechanisms into ecological models to improve predictions of belowground processes, while caution is required when extrapolating these insights to more complex natural ecosystems.</p>