This study was conducted to investigate antimicrobial, antioxidant and anticancer activities of Opuntia humifusa (OH) petal extracts. The methanol and hexane extracts of OH petals showed their highest antimicrobial activity against Clostridium perfringens. The OH petal butanol fraction had the best antioxidative peroxynitrite scavenging activity among OH petal extracts. The DPPH scavenging activity of OH petals was lower than the peroxynitrite scavenging effect. The hexane and methanol fractions at a concentration of 200 μg/mL inhibited proliferation 80% in four kinds of human cervical cancer cells(B16F10, HepG2, HT-29 and MCF-7). In particular, the anticancer effect against B16F10 human skin cancer cells at the same concentration was higher than that in the other cancer cells.