Ten nardosinane-related terpenoids, including five unreported nardosinane-type sesquiterpenoids, parathyrsoidins H-J and linardosinenes D-E, two unusual condensed nardosinanes, named nardosinoids A and B, together with three known related compounds, were isolated from the Xisha soft coral Lemnalia sp. Their structures were elucidated by extensive spectroscopic analysis and comparison of experimental and calculated electronic circular dichroism data. Nardosinoids A and B are the first condensates of two nardosinanes. All these compounds were evaluated for antimicrobial activity in vitro. Nardosinane-type sesquiterpenoids parathyrsoidin I and linardosinene E showed inhibitory effects against influenza A virus H1N1 (IC50 7.1 and 1.1 μM, respectively). In addition, nardosinoids A and B exhibited antibacterial activity against Bacillus subtilis (MIC 4-8 μg/mL).