A fuel injector for heating fuel to be injected into an internal combustion engine. A cylindrical barrel extends between a solenoid and an injection tip for passage of fuel. The outer surface of the barrel supports a suitable circuit pattern formed of an electrically resistive material for generating heat which is passed through the wall of the barrel to warm the fuel which may be stationary or flowing. The electrically resistive material has a positive thermal coefficient, permitting voltage to be applied continuously across the heater causing a current to flow through the heater, the current being inversely proportional to the temperature of the heater. Thus, the heater is self-regulating, the current automatically increasing under cold conditions and diminishing as the fuel injector warms up after starting of the engine. Desirably, the heater is outside both the engine firing chamber and the flow path of the fuel.