A method for controlling a cooling system of a hybrid vehicle comprising at least one combustion engine and one electric motor, the hybrid vehicle being able to assume the following operating modes: - an electric mode, wherein the vehicle is propelled and/or towed by the electric motor without the intervention of the combustion engine; - a thermal mode wherein the vehicle is towed and/or propelled solely by means of the combustion engine without the intervention of the electric motor; - a hybrid mode wherein the vehicle is towed and/or propelled simultaneously by means of combustion engines and electric motors; the cooling system comprising at least: - a high-temperature cooling circuit for cooling the combustion engine and a low-temperature cooling circuit for cooling the electric motor and an associated high-voltage battery, and - a coolant transfer circuit connecting the high-temperature cooling circuit and the low-temperature cooling circuit and comprising regulating means (302, 306) for controlling the circulation of coolant in the transfer circuit, the method for controlling the cooling system in electric mode comprises at least: - an initialization step "E0" consisting in checking the operating parameters linked to driving in electric mode, such as the charge of the high-voltage battery or that the temperature of the battery is higher than the minimum usage temperature (Tu-min), the "E0" initialization step being implemented in particular when the hybrid vehicle is started up, - a step "E1" consisting in determining whether the coolant present in the high-temperature cooling circuit is at a temperature below or above an operating limit temperature (TFmax) of the low-temperature cooling circuit; and - when the temperature of the coolant in the high-temperature cooling circuit is below the operating limit temperature (TFmax) of the low-temperature cooling circuit, a step "E2" consisting in controlling said means (302, 306) for regulating the transfer circuit to assume the open position. - an electric mode, wherein the vehicle is propelled and/or towed by the electric motor without the intervention of the combustion engine; - a thermal mode wherein the vehicle is towed and/or propelled solely by means of the combustion engine without the intervention of the electric motor; - a hybrid mode wherein the vehicle is towed and/or propelled simultaneously by means of combustion engines and electric motors; - a high-temperature cooling circuit for cooling the combustion engine and a low-temperature cooling circuit for cooling the electric motor and an associated high-voltage battery, and - a coolant transfer circuit connecting the high-temperature cooling circuit and the low-temperature cooling circuit and comprising regulating means (302, 306) for controlling the circulation of coolant in the transfer circuit, - an initialization step "E0" consisting in checking the operating parameters linked to driving in electric mode, such as the charge of the high-voltage battery or that the temperature of the battery is higher than the minimum usage temperature (Tu-min), the "E0" initialization step being implemented in particular when the hybrid vehicle is started up, - a step "E1" consisting in determining whether the coolant present in the high-temperature cooling circuit is at a temperature below or above an operating limit temperature (TFmax) of the low-temperature cooling circuit; and - when the temperature of the coolant in the high-temperature cooling circuit is below the operating limit temperature (TFmax) of the low-temperature cooling circuit, a step "E2" consisting in controlling said means (302, 306) for regulating the transfer circuit to assume the open position.