Our knowledge of octocoral diversity in the eastern Pacific has been focused on shallow reef habitats, while the fauna occurring in the mesophotic zone from 40 to 150 m is poorly known. A new species of the gorgoniid Eugorgia was recently obtained with a submersible from the Hannibal Bank, a coastal seamount 60 km off mainland Panama and 15 km from Coiba Island. The morphological characters were analyzed and illustrated by light and scanning electron microscopy. Eugorgia siedenburgae sp. nov. can be distinguished from the other species in the genus by its bushy, multiplanar, bicolored colony, and the sclerites colors, composition, and sizes. This new species increases the number in the genus to 13 and contributes to our understanding of the fragile mesophotic biodiversity.