The present study compares the antitumor activity of extracts from Auricularia auricula-judae, Phellinus gilvus, Ganoderma lucidum, and 100 Korean wild plants in the P388D1 macrophage cell line. The antitumor activity of A. auricula-judae extract (44.21%) did not differ significantly (P < 0.05) from those of Ph. Gilvus (39.46%) and G. lucidum (36.64%) at 1 mg/mL of concentration. Among 100 wild plants, Morus bombycis f. kase, Draba nemorosa var. hebecarpa, Sedum oryzifolium, Lotus corniculatus var. japonicus, and Auricularia auricula-judae 70% ethanol extracts inhibited the viability of tumor cells by 41.85%, 37.31%, 30.29%, 31.98%, and 25.40% at 3 mg/mL of concentration, while inhibition concentration (IC50) values were 1.81, 1.49, 1.05, 1.10, and 0.72 mg/mL, respectively. In Sarcoma 180, NCI H358, and SNU 1 cell lines, the inhibitory activities of A. auricula-judae extract were 65.71%, 69.76%, and 68.01%, respectively. Taken together, the results obtained from the present study indicated that four plant extracts (4% of tested wild plants) and A. auricula-judae extract with similar levels of Ph. Gilvus and G. lucidum extracts may be new potential antitumor agents.