Nine new cembrane diterpenes, named sarcoglaucins A-I (1–9) along with three known analogues, trochelioid (10), 7α-hydroxy-Δ⁸⁽¹⁹⁾-deepoxysarcophine (11), and (−)-sartrochine (12), were isolated from the soft coral Sarcophyton glaucum collected at Xisha Islands in the South China Sea. The structures of all the compounds were established by extensive spectroscopic analysis. The absolute configurations of sarcoglaucins A and B with an unusual [10.3.2.1] cage-type structure were determined using X-ray diffraction and quantum chemical calculation methods. Sarcoglaucin B (2), sarcoglaucin E (5) and compounds 10–12 showed strong antifouling activity against the barnacle Balanus amphitrite.