Medicinal mushrooms have been essential components of traditional Chinese herbal medicines for thousands of years, and they protect against diverse health-related conditions. The components responsible for their anti-inflammatory activity have yet to be fully studied. This study investigates the anti-inflammatory activity of n-hexane, chloroform, ethyl acetate, and methanol extracts of mycelia in submerged culture from 5 commercially available medicinal mushrooms, namely Cephalosporium sinensis, Cordyceps mortierella, Hericium erinaceus, Ganoderma lucidum, and Armillaria mellea. MTT colorimetric assay was applied to measure the cytotoxic effects of different extracts. Their anti-inflammatory activities were evaluated via inhibition against production of lipopolysaccharide (LPS)-induced nitric oxide (NO) in murine macrophage-like cell line RAW264.7 cells. Of the 20 extracts, n-hexane, chloroform, ethyl acetate, and methanol extracts from C. sinensis, C. mortierella, and G. lucidum; chloroform extracts from H. erinaceus and A. mellea; and ethyl acetate extracts from A. mellea at nontoxic concentrations (<300 μg/mL) dose-dependently inhibited LPS-induced NO production. Among them, the chloroform extract from G. lucidum was the most effective inhibitor, with the lowest half maximal inhibitory concentration (64.09 ± 6.29 μg/mL) of the LPS-induced NO production. These results indicate that extracts from medicinal mushrooms exhibited anti-inflammatory activity that might be attributable to the inhibition of NO generation and can therefore be considered a useful therapeutic and preventive approach to various inflammation-related diseases.