Up to now, the comparative analysis of the antioxidant and anticancer activities of the ethyl acetate extracts from fruiting body, mycelial biomass, and culture liquid of Omphalotus olearius are not reported. In this study, antioxidant activity of different samples was compared by six different methods: DPPH and ABTS radical scavenging activities, metal chelating activity, reducing power, inhibition of β-carotene bleaching, and lipid peroxidation through ferric thiocyanate assay. Total phenolic contents of the samples were also determined. The mycelial biomass produced in vitro conditions presented the highest activity by five of them which was following by culture liquid. The potential antiproliferative effects of the extracts in cell culture, human cancer (A549, Caco2 and MCF-7) and healthy (CCD-19LU and CCD 841 CoN) cell lines by WST-1 assay was also evaluated. The highest anticancer effects were determined on A549 lung cancer cells treated with mycelial biomass extract and Caco2 colon cancer cells treated with culture liquid extract. The culture liquid was more effective on the cells than mycelial biomass according to IC50 values. All tested extracts were also evaluated for their toxicity against brine shrimp larvae (Artemia salina). O. olearius culture liquid and mycelial biomass extracts showed highest and lowest toxicity against A. salina, respectively.