The current study compared the physicochemical properties, antioxidant compounds and activities, of unripe and ripe fruits of three cultivars (Seolhyang, Janghee, and Maehyang) of strawberries grown in Korea. As fruits matured, their soluble solids content increased and their organic acid content decreased. Total phenolic content (TPC) and total flavonoid content (TFC) did not differ between Seolhyang and Maehyang fruits, regardless of maturity, whereas unripe Janghee fruits showed higher TPC and TFC than ripe fruits. Total anthocyanin content was higher in ripe fruits than in unripe fruits. For total antioxidant activity, ripe and unripe Seolhyang fruits showed no differences, whereas unripe Janghee fruits showed significantly higher activity than ripe fruits. TPC and TFC were highly correlated, as were DPPH and ABTS radical scavenging activities. Thus, antioxidant contents and total antioxidant activities differed with variety and fruit ripeness at harvest. Unripe fruits show strong potential for use in functional food manufacturing.