The novel 5,10-dihydrophencomycin methyl ester (4) and the known microbial metabolites (2-hydroxyphenyl)-acetamide (1), menaquinone MK9 (II, III, VIII, IX-H8) (2), and phencomycin (3a) were isolated from an unidentified marine Streptomyces sp. and the structures were elucidated by NMR methods. Compound 4 shows weak antibiotic activity against Escherichia coli and Bacillus subtilis.