Objectives: Lentinus edodes is an edible mushroom with a variety of beneficial effects such as antitumor, anti-inflammatory, antioxidant, and immune-modulatory activity. This study was carried out to evaluate the antimicrobial activities of Lentinus edodes extracts against oral-related bacteria. Methods: The antimicrobial activities of this extracts were investigated against S. anginosus, S. sobrinus, S. aureus, S. mutans, S. ratti, S. sanguinis, A. viscosus, A. naeslundii, and A. actinomycetemcomitans by the disc diffusion method, minimum inhibitory concentration (MIC), and growth inhibition. Results: Ethanol extracts had no antimicrobial activities, but acetone extracts showed antimicrobial activities against A. viscosus and A. actinomycetemcomitans and ethyl acetate extracts had effects against S. aureus, S. sanguinis, A. viscosus, and A. actinomycetemcomitans. Conclusions: The inhibitory effect of Lentinus edodes extracts was investigated on the growth of A. viscosus. Ethyl acetate and acetone extracts showed 90% and 77% inhibitory effect, respectively, against A. viscosus for 24 hrs. Ethyl acetate extracts had MIC of 25.0 mg/ml and acetone extracts showed MIC of >25.0 mg/ml.