A self-releasing satellite “pop-up” tag was attached to an adult male shortfin mako captured off of the southeastern United States. The tag was deployed in the spring of 2002 and detached after 60 days in an area approximately 72 km from the tagging location. Archived tag data indicated a depth range of 0 to 556 m in ambient temperatures between 10.4 and 28.6 °C. The shortfin mako demonstrated a diel pattern of vertical movement defined by greater mean depths and larger depth ranges during daylight hours. Depth and temperature data suggested a seasonal behavioral change in vertical movements associated with an increase in sea-surface temperatures during the study period.