This study explores the molecular association between 4-(thiophen-2-yl)-1-(4-(4-(trifluoromethyl)phenyl) piperazin-1-yl)butan-1-one (RTC1), an antidiabetic compound recently reported by our research group with challenging aqueous solubility, and 2-hydroxypropyl-β-cyclodextrin (HPBCD). The formation of a RTC1/HPBCD complex resulted in improved solubility. A phase-solubility diagram was used to determine the complex stability constant and stoichiometric ratio. 2D 1 H NMR spectroscopy was utilized to study the molecular interaction between RTC1 and HPBCD in the complex. Differential scanning calorimetry and scanning electron microscopy was also employed to confirm complex formation. In vitro biological evaluation, using a glucose uptake assay, showed that the homogeneous RTC1/HPBCD complex solution showed the same activity to that of RTC1 alone, with no reduction in activity due to the presence of HPBCD.