Barley leaf grown under light-emitting diode (LED) light was prepared and investigated for its free radical scavenging activity. LED light such as red, far-red, blue, blue-red, green, yellow, UVA, and white and also fluorescent light and dark conditions were also used in this study. Length and weight of barley leaves were measured and the Hunter color value, DPPH radical scavenging activity, and ABT radical-scavenging activity of barley leaf extracts were estimated. Extraction of barley leaf was performed by using a 70% ethanol solution. Length of barley leaf grown with red and green LED was 9.9 and 12.6 cm, respectively. Hunter $L^*$ and $a^*$ values of extracts of barley leaf grown under dark conditions were higher than those of other LED light-treated samples. The DPPH radical scavenging activity of extracts of barley leaf grown with blue, UVA, and under dark conditions were 41.40, 36.23, and 43.57%, respectively. ABT radical scavenging-activity of extracts of barley leaf grown under LED of red, far-red, blue, blue-red, green, yellow, and white were 5.46, 6.10, 6.00, 5.93, 5.74, 6.32, and $5.94;{mu}mol;TE;g^{-1}$, respectively.