Bali sardinella (Sardinella lemuru) is a type of fish that significantly contributes to the Pengambengan Nusantara Fishing Port (NFP). However, there has been a decline in lemuru production. This decline in production is closely related to its food sources, namely phytoplankton and zooplankton. Plankton plays a crucial role in the ecosystem as it forms the foundational link in the food chain. This research aimed to identify types of plankton the dietary preferences of S. lemuru in Pengambengan NFP. Samples were taken from the S. lemuru size groups 'lemuru' (sized 15–18cm) and 'lemuru kucing' (sized >18cm), during May and June 2023. The research method employed was descriptive qualitative. Plankton identification was carried out at the Aquaculture Laboratory, Marine and Fisheries Polytechnic of Jembrana. The result of S. lemuru stomach contents revealed a higher presence of zooplankton compared to phytoplankton. The identified plankton composition includes five orders of zooplankton (Calanoida, Harpacticoida, Euphausiacea, Amphipoda, and Cyclopoida), fish eggs, one genus of phytoplankton (Ceratium sp.), and one family of Bacillariaceae.