Droughts are, and are predicted to be, more intense and frequent as consequences of climate change, particularly in mountainous regions. This is exacerbated by factors such as reduced winter snowpack, as observed in the French Alps in 2022. Here, we examine how the impact of a summer drought affects the soil microbiome, its functioning, and the consequences for soil organic carbon (C) cycling—these represent key uncertainties in predicting the fate of carbon in a warming world. To investigate, we established a mesocosm experiment at the Lautaret station (2060m above sea level) to explore how drought may alter the soil microbiome composition, functioning, and the carbon cycle. During the summer of 2023, a short-term mesocosm experiment (4 months) was conducted, simulating a centennial drought with two episodes of heavy rainfall (summer storms). Soil cores (0-30cm) were sampled from a mountain catchment at the Col du Lautaret, France. The cores were then subjected to drought or control treatments in a lysimeter within a paired experimental design (16 mesocosms, 4 replicates) over four months. We monitored soil functioning throughout the experiment using six soil campaigns to evaluate: (i) soil microbial fungal and bacterial community composition using amplicon sequencing of the 16S rRNA gene and ITS, (ii) soil extracellular enzymes involved in the C, N, and P cycles through the decomposition of soil organic matter, (iii) soil metabolomics, (iv) soil microbial biomass (chloroform fumigation), and (v) carbon fluxes, measuring Net Ecosystem Exchange as well as losses through carbon leachates following heavy rainfall events. Preliminary results indicate that the drought shifted the soil from acting as a carbon sink (control, positive NEE) to a carbon source (drought, negative NEE). Insights into microbial functioning and composition will help to elucidate this change in carbon cycling dynamics. Sampling at the end of the experiment—after shelters had been removed for one month—revealed that the microbiome had not fully recovered from the drought treatment, as microbial biomass was significantly lower in the treated plots. With this experimental and interdisciplinary approach, we aim to provide new insights into how extreme weather events influence soil microbial dynamics and the implications for carbon in mountain regions that are experiencing rapid climate warming.