The results of rigorous modeling of phase solubility diagrams, pH solubility profiles and potentiometric titrations revealed the following for benzimidazole (BZ) and BZ/β-CD complexation in aqueous solution: (a) the pKa value of BZ estimated at 5.66 ± 0.08 was reduced to 5.33 ± 0.06 in the presence of 15 mM β-CD at 25 °C, thus indicating inclusion complex formation; (b) BZ forms soluble 1:1 and 2:1 BZ/β-CD complexes with complex formation constants K11 = 104 ± 8 M-1 and K21 = 16 ± 6 M-1; (c) protonated BZ forms only 1:1 complex with K11 = 42 ± 12 M-1; (d) 1H-NMR studies in D2O showed significant upfield chem. shift displacements for inner cavity β-CD protons indicating inclusion complex formation, while (e)mol. modeling of BZ-β-CD interactions in water clearly indicated complete inclusion of one BZ mol. into the β-CD cavity.