Experimental molar solubility of clonazepam and diazepam in binary and ternary mixtures of polyethylene glycol 200 (PEG 200), propylene glycol (PG), and water (116 data points) along with the density of saturated solutions at 298.2 K were reported. Also, the experimental solubilities of clonazepam and diazepam in the monosolvents of PEG 200, PG, N-methyl pyrrolidone (NMP), ethanol (EtOH), and water at five different temperatures, (298.2, 303.2, 308.2, 313.2, and 318.2) K (50 data points), have been reported. The Jouyban-Acree model was used to fit to the measurements for providing a computational method. Employing the solubilities in the neat solvents, the measured solubilities were back-calculated, and the overall mean percentage deviations (OMPDs) of the model were 21.4 % and 19.5 % for clonazepam and diazepam, respectively. An addition of the Hansen solubility parameters to the model helps us to train all of the data sets (clonazepam and diazepam) at once, and the back-calculated OMPD was 20.7 %.