Al_0.2CoCrFeNiSc_x (x=0, 0.1, 0.2 and 0.3, molar fraction) alloys were prepared by arc melting. The effects of Sc addition on the microstructure, phase evolution and mechanical properties of Al_0.2CoCrFeNiSc_x alloys were investigated. The results showed that Sc could refine grain size, change phase type and improve mechanical properties. The grain size of Al_0.2CoCrFeNiSc_0.3 alloy (8.5 μm) was reduced by approximately 50.6% compared to that of Al_0.2CoCrFeNiSc_0.1 alloy (17.2 μm). The crystal structure evolved from a single FCC phase to a mixed phase including two types of FCC phases and one type of BCC phase. The FCC phase mainly appeared in the regions of (Co, Cr, Fe)- rich dendrites and (Ni, Sc)-rich interdendrites; while the BCC phase was mainly located in the region of (Al, Ni)-rich interdendrites. The yield strength increased from 167 to 717 MPa as the x value in Al_0.2CoCrFeNiSc_x alloy increased from 0 to 0.3, improved by 329.3%, which could be attributed to grain size strengthening, solid solution strengthening and phase evolution.