The impact of fermentation and bud size on the antioxidant activity, total phenolic content (TPC), and bioactive compounds of caper buds were investigated. The results showed significant differences in the bioactive properties depending on bud sizes and fermentation process. Antioxidant activity values of fresh caper buds were ranged between 69.61% (bid size) and 72.78% (small size), whereas the values of fermented ones varied between 12.50% (big size) and 39.09% (small size). TPC of fresh caper buds were found in the range of 357.81 mg GAE/100 g (medium size) and 372.22 mg GAE/100 g (small size), while those of fermented buds were ranged from 167.53 mg GAE/100 g (medium) to 246.01 mg GAE/100 g (small). Apigenin-7-glucoside, (+)-catechin, 1,2-dihydroxybenzene, and 3,4-dihydroxybenzoic, syringic, and gallic acids were the major phenolic compounds in both fresh and fermented caper buds. Overall, this study clearly demonstrated that both fermentation process and bud size significantly affected the antioxidant activity, TPC, and phenolic compounds of caper buds.