This is the first taxonomic study of marine and estuarine free-living nematodes conducted in Sarawak coastal waters, Malaysia. A total of 111 species, representing 47 genera and 20 families were identified from 24 study sites along the Sarawak coastal waters. All species are first recorded in Sarawak and were grouped according to their habitat (sediment type). All species were described and illustrated with detailed taxonomic notes and discussions. Pictorial keys of identification for species were also produced.