Metal nitrides are potential electrode materials for supercapacitors because of their high conductivity, high capacitance and good corrosion resistance. Herein, we present a general strategy to prepare self-standing bimetallic nitride thin film nanostructures using magnetron co-sputtering and further to boost their electrochemical performance for supercapacitors. Using niobium titanium nitride (TiNbN) as an example, we show that the synergy of Ti and Nb greatly boosts the capacitive performance to a high specific capacitance of up to 59.3 mF cm−2 at 1.0 mA cm−2, along with outstanding cycling stability for at least 20000 cycles. We further demonstrate an all metal nitride based asymmetric device by combing TiNbN with a vanadium nitride (VN) negative electrode. The asymmetric device operates at a voltage window of 1.6 V and achieves a maximum energy density 74.9 mWh cm−3 at a power density of 8.8 W cm−3. Our work not only presents a first demonstration of employing TiNbN as supercapacitor electrode material, but also opens up new possibility for the rational construction of all nitride based high performance asymmetric supercapacitors.