Mesophotic coral reef ecosystems are notoriously undersurveyed worldwide and particularly in remote locations like the Northwestern Hawaiian Islands (NWHI). A total of 37 mixed-gas technical dives were performed to depths of 80 m across the NWHI to survey for the presence of the invasive octocoral Carijoa sp., the invasive red alga Acanthophora spicifera, and conspicuous megabenthic fauna such as black corals. The two invasive species were not recorded from any of the surveys, but two commercially valuable black coral species, Antipathes griggi and Myriopathes ulex, were found, representing substantial range expansions for these species. Antipathes griggi was recorded from the islands of Necker and Laysan in 58 – 70 m, and Myriopathes ulex was recorded from Necker Island and Pearl and Hermes Atoll in 58 – 70 m. Despite over 30 yr of research in the NWHI, these black coral species had remained undetected. The new records of these conspicuous marine species highlight the utility of deep-diving technologies in surveying the largest part of the depth range of coral reef ecosystems (40 – 150 m), which remains largely unexplored.