Tectonic changes in the Southern Ocean likely triggered global cooling across the Eocene, yet the evidence for when the Drake Passage opened remains ambiguous. This climatic-tectonic change likely impacted marine ecosystems, including sharks that inhabited high-latitude regions. The fossil record could provide insights into sharks’ response to global cooling over the Eocene, but paleoecological studies are few. The Middle-to-Late Eocene units on Seymour Island provide a rich, diverse fossil record, including that of sharks. We analyzed the oxygen isotope composition of phosphate from shark tooth bioapatite (δ¹⁸O_p) and compared to results of co-occurring bivalves and predictions from an isotope-enabled global climate model output to investigate habitat use and environmental conditions. Bulk δ¹⁸O_p values (mean 22.0 ± 1.3‰) show no significant changes through time, and variation exceeds that in simulated seasonal and regional values. Pelagic and benthic taxa exhibit similar values across units but are offset relative to bivalve and modeled δ¹⁸O_p values. Some taxa suggest movements into warmer water (e.g., Otodus) or deeper, colder waters (e.g., Pristiophorus). Taxa like Raja and Squalus display no shift, tracking seasonal signals in Seymour Island. The lack of difference in δ¹⁸O_p values between pelagic and benthic sharks in the Late Eocene likely indicates that sharks ventured as far as the Drake Passage. Our findings demonstrate that sharks usually track preferred conditions in their tooth bioapatite instead of acting as passive tracers that record environmental signals in a single location.