The authors report on above-room-temperature operation of InAsAlGaSb quantum cascade lasers emitting at 12 μm. The laser structures are grown on a n-InAs (100) substrate using solid-source molecular beam epitaxy. An InAsAlGaSb superlattice is used as an active part and an InAs double plasmon waveguide is used for optical confinement. Results show that increased doping concentration in the injection part of the active region expands the current operation range of the devices, allowing laser operation at and above room temperature. The observed threshold current density is 4.0 kA cm2 at 300 K; the maximum operation temperature is 340 K.