Two new compounds, 10-dehydroxymelleolide D (1) and 13-hydroxymelleolide K (2), along with seven known compounds, 5'-O-methylmelledonal (3), melleolide D (4), 13-hydroxydihydromelleolide (5), melleolide (6), armillarinin (7), armillaridin (8), and armillarikin (9), were isolated from the culture broth of Armillaria sp. Their structures were determined by spectroscopic data analysis. All the compounds inhibited plant growth of lettuce. Melleolide (6) and armillarikin (9) inhibited mycelial growth of Coprinopsis cinerea and/or Flammulina velutipes.