<p>Finless porpoises (FPs) serve as flagship species and key ecological indicators for assessing environmental quality. However, FPs are challenging to survey due to their elusive behavior and lack of distinctive features. Stranding and sighting events offer essential information on species diversity, distribution patterns, and potential threats. In this study, records from 1986 to 2023 were analyzed to assess the temporal and spatial distribution patterns of FP strandings and sightings in the Qiantang River Estuary, China. Results show an increase in the number of recorded events over time. Seasonal variations were evident, with a peak in strandings and sightings occurring in late winter. The frequency of records was higher during spring and moderate tides compared to neap tides, particularly in hydrologically normal years. Rapidly receding tides and sediment accumulation appear to restrict the activity space of FPs, thereby increasing the frequency of these events. Localized conditions associated with stranding and sighting events were classified into four categories: bifurcation zones, confluence zones, separation zones, and deep channels adjacent to concave banks. Deep channels, which are optimal for shipping, also elevate the risk of FP strandings. These findings offer valuable insights for the development and design of conservation strategies tailored to the needs of FPs in estuarine environments.</p>