Development of oil palm plantations on peatland requires drainage for water level regulation which often creates new artificial habitats for aquatic inhabitants. We assessed the changes in fish communities of the artificial drainage systems in Betong, Sarawak. Fish were sampled from three sampling stations at the manmade drainage from July 2013 until July 2019. A total of 1546 individuals represented by 12 species were recorded across oil palm plantation development phases. Although it is an artificial habitat, the conversion of logged peat swamp forest to cleared land reduced fish species richness by at least 25%. Not many changes were observed when the land was initially planted with palms. As the oil palm reached 2 years old, fish species richness increased and was comparable to the prior conversion phase. The fish abundance fluctuated as the peat swamp forest was being cleared, and throughout the oil palm development phases.