The aim of this work is to determine the theta temperatures of chlorinated poly(propene) solutions. The cloud point temperatures of chlorinated poly(propene) in ethyl acetate, butanone, and 1,4-dioxane solutions were determined at various concentrations. The theta temperatures of chlorinated poly(propene) solutions were determined by the linearity of the reciprocal cloud point temperature against the logarithm of the polymer volume fraction. The theta temperatures of chlorinated poly(propene) in ethyl acetate, butanone, and 1,4-dioxane solutions are 353.11 K, 347.95 K, and 335.91 K, respectively. The theta temperature increases with the decrease of solubility. The lower the solubility of chlorinated poly(propene) in solvent, the larger is the free energy of mixing, the weaker is the spontaneous dissolution, and the higher is the theta temperature.