Purpose <p>This study compares the metazoan parasite communities of the banded croaker <i>Paralonchurus brasiliensis</i> in Sepetiba Bay, southeastern Brazil, across a two-decade interval.</p> Methods <p>A total of 193 fish were examined: 93 individuals sampled between September 2001 and March 2002 (previously published dataset) and 100 individuals collected between May and August 2022. Parasites were identified using standard parasitological procedures, and community descriptors were recalculated to allow direct comparison between sampling periods. Differences in parasitological indices and community structure were assessed using univariate and multivariate analyses.</p> Results <p>Eighteen parasite species were recorded, with eleven occurring in both sampling periods. Four crustacean taxa represent new host records for <i>P. brasiliensis</i>. A shift in parasite functional structure was detected: adult endoparasites predominated in 2001, whereas larval endoparasites dominated in 2022. Significant declines were observed in the prevalence and abundance of <i>Aponurus pyriformis</i> and <i>Procamallanus (Spirocamallanus) pereirai</i>, and mean species richness and diversity indices were lower in 2022. While nMDS revealed partial overlap in community composition, PERMANOVA indicated statistically significant temporal differences.</p> Conclusion <p>The results reveal a simplification of parasite communities and a decline in key taxa across two decades, consistent with environmental disturbance in Sepetiba Bay. These findings highlight the value of parasite assemblages as indicators of ecological change and underscore the need for integrated parasitological and environmental monitoring.</p>