The Western Palaearctic moth Cataclysta lemnata (Linnaeus, 1758) is considered one of Europe’s most common water moths. However, there are limited data regarding the larval stages, particularly in eastern and southeastern Europe. During the 2017-2021 aquatic macroinvertebrate survey, C. lemnata was detected at seven sites in the Pannonian region of Serbia. All sightings were of the larval/aquatic phase and originated from both heavily polluted habitats and relatively unpolluted waterbodies. A consistent feature at all sites is duckweed (Lemna sp.), confirming the preference of C. lemnata for this plant. Our findings contribute to a better understanding of the presence of this species in the region and suggest that it may be more abundant in its various aquatic habitats. As the adult stages are simpler to identify, and with the advent of public online databases (Alciphron, biologer.rs), there have been multiple records of adult moths in recent years. Regarding the aquatic stages, there is a need for more comprehensive surveys with a primary emphasis on suitable habitats throughout the region and the use of molecular methods for the identification of early larval stages would be beneficial.