Five new phenethylamine (PEA) derivatives (1-5) were isolated from the strain of Arenibacter nanhaiticus sp. nov. NH36A(T) derived from the marine sediment of the South China Sea by bioassay-guided fractionation. Their structures were elucidated by spectroscopic methods including UV, IR, HR-MS and NMR. Interestingly, compounds 1-4 existed as enantiomers, which were resolved by chiral liquid chromatography. The resolved configuration of each enantiomer was assigned by the Marfey's method. Of these compounds, 5 showed weak antimicrobial activity against Staphylococcus aureus and Bacillus subtilis with MIC values of 0.50 and 0.25 mg ml(-1), respectively.