A fuel injector, preferably a dual fuel injector, for an internal combustion engine is disclosed. The fuel injector comprises first and second valve needles (80, 100) arranged to control the injection of first and second fuels, first and second control chambers (88, 10) associated with the first and second valve needles (80, 100) respectively, a first control valve (26) comprising a first control valve member (48) and arranged to vary the pressure of a control fluid in the first control chamber (88) so as to cause opening and closing movement of the first valve needle (80), and a second control valve (28) comprising a second control valve member (60) and arranged to vary the control fluid 10 pressure in the second control chamber (110) so as to cause opening and closing movement of the second valve needle (100). The first and second control valve members (48, 60) are arranged for linear movement along a common control valve axis.