In the eastern Pacific Ocean, the genus Thesea has only been reported off Isla del Coco, Costa Rica, and La Jolla, California. Herein we describe a new species of Thesea from the threatened mesophotic zone of Hannibal Bank seamount and report the occurrence of the genus in Panama. The morphological characters of the species were analyzed and illustrated by optic and scanning electron microscopy. Thesea dalioi sp. nov. can be distinguished from the only other eastern Pacific species, Thesea variabilis (Studer, 1894), in the colony shape, branch thickness, prominent polyp mounds, bright red color of the colony and sclerites, and the size and composition of sclerites. This new species represents the second published report for the genus in the region and contributes to our understanding of the diversity and distribution of the octocorals from the mesophotic zone in the eastern Pacific Ocean.