This research aimed to investigate the antibacterial activity of Lycoris radiata. The methanol extract and solvent fractions from L. radiata exhibited antibacterial activities against Escherichia coli, Staphylococcus aureus, and Helicobactor pylori. Open-column chromatography was used to isolate phytochemical constituents from L. radiata; spectroscopic analysis elucidated their structures as ${eta}$-sitosterol (1), daucosterol (2), O-methyllycorenine (3), lycorenine (4), lycoricidinol (5), lycorine (6), and lycoricidine (7). Further testing of compounds 1 - 7 revealed antibacterial effects against E. coli, S. aureus, and H. pylori, which suggested the potential of these substances as antibacterial agents. We determined that compounds 1 and 2, isolated from the n-hexane fraction, were more effective against S. aureus and H. pylori. Compound 4, isolated from the methylene chloride fraction, exhibited noticeable antibacterial effects against E. coli. This study is the first report on the antibacterial activities of phytochemical constituents from L. radiata against E. coli, S. aureus, and H. pylori.