Mangroves are recognised as important nursery and feeding areas for resident and inshore fish species. However, the importance of West African mangroves to the life cycle of fish communities remains poorly studied. The present study is the first record of fish species in tropical insular mangroves for this region and its aim was to assess habitat usage by fish species. Two mangroves of São Tomé Island (Praia das Conchas and Malanza) were sampled with a multihabitat approach and using different fishing gear to maximise the diversity of fish species collected. Several environmental parameters were also measured. Both mangroves are nursery and opportunistic feeding grounds for fish species, as well as settlement areas for resident species. The highest number of both juveniles and adults (inshore and residents) was observed at the Malanza mangrove, which is also the largest and has the highest habitat heterogeneity. Four new occurrences were reported for the São Tomé and Principe area, namely Pomadasys jubelini, Bostrychus africanus, Dalophis cephalopeltis and the introduced species Oreochromis mossambicus.