Coastal cetaceans in Southeast Asia are poorly studied and are particularly vulnerable to anthropogenic threats, especially in intensive fishing grounds. To investigate the distribution and habitat characteristics of cetaceans in the productive coastal waters of Matang, Perak, Malaysia, boat‐based line transect surveys were conducted between 2013 and 2016. The Irrawaddy dolphin (Orcaella brevirostris) was most frequently encountered at 3.87 sightings per 100 km, followed by the Indo‐Pacific finless porpoise (Neophocaena phocaenoides) at 1.72 sightings per 100 km, and the Indo‐Pacific humpback dolphin (Sousa chinensis) at 0.66 sightings per 100 km. The mean group size was largest for humpback dolphins (8.4 individuals), followed by Irrawaddy dolphins (6.4 individuals), and finless porpoises (2.8 individuals). Humpback dolphins exhibited a clustered distribution concentrated mainly in shallow estuarine waters (<10 m deep and <5 km from river mouths), whereas Irrawaddy dolphins were more widely distributed in farther coastal waters (<15 m deep and <15 km from river mouths), and finless porpoises were mostly found farthest from the shore in coastal waters (10–25 m deep and >15 km from river mouths). The spatial distribution of the three cetaceans overlapped minimally, and this is likely to reflect the distribution of preferred prey resources, species interactions, and their differential responses to anthropogenic activities and species dominance. The results from our study serve as baseline information for future research, conservation, and habitat management of these vulnerable and endangered coastal cetaceans. Conservation actions are recommended for the Matang area.

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Relatively little is known about spinner dolphins in Malaysian waters and the wider Southeast Asian region. This note represents the first known acoustic recording of the species sighted opportunistically in the northern Straits of Malacca. Over a brief 20 min sighting, 46 whistles were recorded and four tonal types were detected, with 54.4% being upsweep whistles. The whistle duration ranged from 36 to 977 ms and the frequency ranged from 6.6 to 23.8 kHz. Fifty-seven click trains with a mean interclick interval of 41.5 ± 19.3 ms were detected. These findings provide a baseline for future regional acoustic research on this species.