The aim of this experiment was to assess the effects of N addition alone, and in combination with P and K, on the diversity, structure and function of mangrove soil microbial communities, with a focus on bacterial communities, these being the dominant component of the microbial biomass of mangrove soils (Chen et al. 2016). A laboratory based, controlled soil incubation experiment enabled us to focus on soil microbial responses to nutrient enrichment by removing plant-mediated responses and potential impacts of other fluctuating environmental variables on microbial communities. We sought to identify which bacterial groups change with nutrient addition, and to link this with observed changes in microbial functioning. As mangrove soils experience both aerobic and anaerobic conditions, each with their own distinct microbial communities, we incubated soil in two different oxygen environments to compare responses. This information will improve our understanding of microbial responses to elevated nutrients and the potential implications for C storage and nutrient cycling in mangrove environments.