The resident population of Burrunan dolphins (Tursiops australis) in Port Phillip Bay (PPB), Victoria, consists of approximately 150 individuals. While previous studies suggested a limited southern distribution, little is known about their full range across the bay. This study examines the spatiotemporal distribution of Burrunan dolphins across four zones representative of PPB’s benthic habitats and bathymetry to identify key habitat drivers. Over 129 boat-based surveys conducted between March 2015 and August 2021, with 181 dolphin sightings recorded. Generalized linear models (GLMs) were used to analyse annual, seasonal, and zonal variations. Results showed no annual variation but significantly higher sighting frequencies in summer and winter compared to autumn. Dolphins were recorded throughout PPB, with a notable preference for the southern zone. Bathymetry and benthic habitat appeared to influence distribution, with dolphins favouring depths of 5–10 m and 10–15 m. These findings expand the known range of the Burrunan dolphin population and highlight the importance of these habitats. We recommend extending marine protected areas in both northern and southern PPB to support conservation. This research enhances our understanding of vital habitat use and provides evidence-based recommendations for future conservation and management of this unique dolphin population.