Yellowfin tuna (Thunnus albacares) are a highly mobile species distributed throughout global tropical and temperate waters. Previously, most of the tagging efforts on yellowfin tuna was concentrated in the northern hemisphere, or across their tropical and subtropical distributions. We deployed pop-up satellite archival tags on 14 yellowfin tuna across their southern latitudinal extent to investigate their behaviour and habitat use in cooler waters. We determined that yellowfin tuna from New South Wales inhabited substantially cooler waters than individuals from tropical and subtropical waters, with their southern distribution seemingly restricted by the East Australian Current. Meanwhile, vertical behaviour was mostly restricted to the upper ocean, with only 1% of depth measurements beyond 200 m. Despite this, ‘extreme’ dives were observed from 62% of tagged tuna, with one individual diving to over 1,250 m. These extreme dives, along with crepuscular movements, were interpreted as potential forage or navigation-driven behaviours. As Western Boundary Currents strengthen and oceans warm, the temporal persistence of tuna towards their latitudinal extents may increase. With yellowfin tuna accounting for approximately 25% of global tuna catch, predicting how their distributions may change with warming waters is especially important for many commercial fisheries. Contrasting habitat use across ecological contexts informs adaptive fisheries management to better anticipate how tuna respond to changing environmental conditions.