The solubilities of piroxicam in binary and ternary mixtures of polyethylene glycols 200 or 400 with ethanol and water (138 data points) at 298.2 K were determined and mathematically represented by cosolvency models. The solubilities were measured using the shake flask method and the models are used to fit the solubility data of piroxicam in the solvent mixtures. The overall mean relative deviations (OMRDs %) for fitting the solubility data of piroxicam in binary and ternary mixtures using the Williams-Amidon and Jouyban-Acree models are 30.7 and 26.8 %, respectively, and the OMRD % values for predicting the solubilities of piroxicam by the trained versions of the Jouyban-Acree model is 57.3 %.