A thermostat assembly for heater devices, in particular for radiators and heaters, comprising: - electronic thermoregulation means configured to activate and deactivate the heating of the heating means adapted to flow inside said heater device; - a casing which defines a cavity adapted to accommodate said electronic thermoregulation means and comprising first mechanical coupling means, said first mechanical coupling means comprising a substantially cylindrical seat; - a probe for detecting the temperature value of said heating means comprising: - second mechanical coupling means complementary to said first mechanical coupling means of said casing to allow the coupling of said probe to said casing, said second mechanical coupling means comprising a substantially cylindrical body projecting from said probe and configured to be coupled by interference with said seat of said first mechanical coupling means; - electrical connection means for the connection to said electronic thermoregulation means; - third mechanical coupling means configured to allow the connection of said probe to an inlet mouth of said heater device; when said probe is coupled to said casing, said first mechanical coupling means and said second mechanical coupling means being configured to allow the rotation of said casing with respect to said probe according to an axis of rotation; characterized in that at least a first annular housing is defined in said seat and at least one projecting body at least partially annular is defined in said cylindrical body or at least a first annular housing is defined in said cylindrical body and at least one projecting body at least partially annular is defined in said seat; said projecting body being adapted to be arranged in said first annular housing when said probe is coupled to said casing so that the fitting of the projecting body in the first annular housing prevents the decoupling of said probe from said casing but does not prevent said rotation of said casing with respect to said probe. - electronic thermoregulation means configured to activate and deactivate the heating of the heating means adapted to flow inside said heater device; - a casing which defines a cavity adapted to accommodate said electronic thermoregulation means and comprising first mechanical coupling means, said first mechanical coupling means comprising a substantially cylindrical seat; - a probe for detecting the temperature value of said heating means comprising: - second mechanical coupling means complementary to said first mechanical coupling means of said casing to allow the coupling of said probe to said casing, said second mechanical coupling means comprising a substantially cylindrical body projecting from said probe and configured to be coupled by interference with said seat of said first mechanical coupling means; - electrical connection means for the connection to said electronic thermoregulation means; - third mechanical coupling means configured to allow the connection of said probe to an inlet mouth of said heater device; - second mechanical coupling means complementary to said first mechanical coupling means of said casing to allow the coupling of said probe to said casing, said second mechanical coupling means comprising a substantially cylindrical body projecting from said probe and configured to be coupled by interference with said seat of said first mechanical coupling means; - electrical connection means for the connection to said electronic thermoregulation means; - third mechanical coupling means configured to allow the connection of said probe to an inlet mouth of said heater device;