The objectives of this study are to enhance the oral bioavailability of cilostazol (CLZ), which is a poorly soluble compound, by cocrystallization and to evaluate the correlation between the calculated solubility of the cocrystal by the solubility product (K sp ) and the complexation constant (K 11 ) and the performance of the cocrystal. Cocrystals of CLZ with 4-hydroxybenzoic acid (4HBA), 2,4-dihydroxybenzoic acid (2,4DHBA), and 2,5-dihydroxybenzoic acid (2,5DHBA) were prepared. Stoichiometric 1:1 structures were formed in the crystal packing of the three cocrystals according to single crystal X-ray diffraction. The calculated solubilities of the CLZ−4HBA cocrystal, CLZ−2,4DHBA cocrystal, and CLZ− 2,5DHBA cocrystal were 9.5-fold, 14.5-fold, and 34.3-fold higher than that of CLZ, respectively. Interestingly, the supersaturated dissolution profile in the nonsink condition was inversely correlated with the calculated solubility of the cocrystals, and the CLZ− 4HBA cocrystal, which mildly enhanced the solubility compared to the other cocrystals, effectively prolonged the supersaturation. The in vivo performance correlated with the in vitro dissolution profile, and the bioavailability of the CLZ−4HBA cocrystal in beagles was also significantly enhanced even when compared to the amorphous solid dispersion. The cocrystallization of CLZ could be an effective means to enhance the bioavailability, but excessive solubility enhancement was not preferable for the CLZ cocrystal.