A specimen of Hippocampus denise (Syngnathidae) recently collected from the outer Great Barrier Reef, Queensland, constitutes the first record of this species from Australian waters. Counts and proportional measurements confirm the identity of the specimen. It was taken by ROV at a depth greater than previously reported for the species and from a new host species of octocoral. We postulate that one reason for the species having previously evaded detection in the region is due to the paucity of knowledge of Australian mesophotic reef systems and briefly discuss the implications of this on assessing the species’ conservation status.