The character of phase transitions in the inclusion compounds of thiourea with pyridinium iodide and nitrate has been analyzed, and a model of ferroelectricity of these compounds has been proposed. Analysis of the temperature dependence of specific heat and intensity of the Bragg peaks has shown that the ferro-paraelectric phase transitions are continuous, in contrast to the nonferroelectric phase transitions. The ferroelectricity of the inclusion systems studied is of the mixed type and has a displacement component and an order−disorder component.