The important role of fruits in human health and nutrition has been better understood with the recent studies on biochemical contents of fruits having antioxidant properties. Being one of the similar studies, in this study, total antioxidant capacity (TAC), phenolic compound, organic acid, and vitamin C contents of three plum species (Prunus domestica L., Prunus cerasifera Ehrh., and Prunus spinosa L.) grown in Van locality (Turkey) were identified, and the correlation between the measured values was investigated. Phenolic compound, organic acid, and vitamin C contents were determined by high-performance liquid chromatography (HPLC) method. Analysis of phenolic compound indicated that chlorogenic acid was the predominant phenolic compound, and the highest value was measured in P. spinosa L. as 12.985 mg kg−1. Malic acid was the predominant organic acids and the highest value was measured in P. spinosa L. as 1.245 g 100 g−1. The highest TAC and vitamin C contents were also measured in P. spinosa L. as 1.021 mmol TE kg−1 and 25.492 mg 100 g−1, respectively. P. spinosa L. was found to be superior to the other two species with respect to antioxidant capacity and other biochemical contents. A significant (P ≤ 0.01) and positive correlation was reported between antioxidant capacity and vitamin C content.