The experimental solubility of tadalafil in binary mixtures of ethanol (EtOH) + water, propylene glycol (PG) + water, polyethylene glycol 200 (PEG 200) + water, polyethylene glycol 400 (PEG 400) + water, and ternary mixtures of PEG 200 + PG + EtoH at 298.2 K were assessed. The experimental data were fitted to the Jouyban Acree model. The mean percent deviations (MPD) of the back-calculated solubilities for EtOH + water, PG +water, PEG 200 + water, PEG 400 + water, and PEG 200 + PG + EtOH mixtures were 7.4%, 11.3%, 14.0%, 18.5%, and 5.6%, respectively and the overall MPD was 11.0%.