Estrogen mediates fast signal responses or transcriptional events via G protein-coupled estrogen receptor 1 (GPER1). However, there is no data on the effect of GPER1 on lung cancer cell proliferation and apoptosis. The present study aimed to analyze the anticancer effects of the GPER1 agonist G.1 on A549 human lung cancer cells. A549 cells were treated with 17ƒÀ.estradiol and G.1, and cell proliferation was analyzed using MTT and WST assays. In addition, the apoptotic effects induced by G.1 were investigated using acridine orange/ethidium bromide staining. A549 cells were treated with a half maximal inhibitory concentration of G.1 for 72 h, and nitric oxide (NO) levels and superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx) enzyme activities were analyzed by spectrophotometry. The results revealed that G.1 significantly decreased cell proliferation. In addition to the antiproliferative effect of G.1, a marked increase in apoptotic activity was observed when cells were treated with 2x10.5 M G.1. Furthermore, G.1 increased NO levels, and SOD and GPx activity. These findings indicate that the GPER1 agonist G.1 is able to exert antiproliferative and proapoptotic effects on A549 cells, and that oxidant and antioxidant molecules may mediate these effects.