In this study, we assessed antioxidant, anti-diabetic, and anti-Alzheimer activities of Opuntia ficus-indica var. saboten (OFI) at harvest time. OFIs were cultivated December 2015~November 2016 in Jeju island. The 70% ethanol extracts of OFI were used to investigate total polyphenol and flavonoid contents, antioxidant(DPPH and ABTS radical scavenging assay), anti-diabetic(yeast α-glucosidase and rat α-glucosidase inhibition assay), and anti-Alzheimer(Acetylcholinesterase and butyrylcholinesterase inhibition assay) activities. Total polyphenol and flavonoid contents of OFIs were 17.40~23.11 μg garlic acid/mg Ex and 2.17~6.22 ug (+)-catechine/mg Ex, respectively. DPPH and ABTS radical scavenging activity of OFIs were 131.98~184.90 mg ascorbic acid(AA) eq/100 g and 63.60~101.83 mg AA eq/100 g, respectively. In the anti-diabetic and anti-Alzheimer activities, 70% ethanol extracts of OFI exhibited moderate inhibition activity, compared to control (acarbose and beberine). Total polyphenol and flavonoid contents, antioxidant, anti-diabetic, and anti-Alzheimer activities were no significant differences by season, respectively. Therefore, information on comparative biological evaluations of OFI may be a beneficial in exploring functional food and drug development.