This paper presents the results of micromechanical failure analyses of titanium metal matrix composite shafts, under cyclic torsional loading. Two different fibre orientations were used to investigate the failure mechanisms, namely +45° and ±45° fibre orientations. The fracture surfaces, after fatigue testing, were examined using a scanning electron microscope. Evidence was found of the existence of both ductile failure which occurred in the matrix material and brittle failure which occurred in the fibres. These modes of failure both played important roles in the overall shaft failure for a +45° fibre orientation. In the case of the ±45° fibre orientation, failure of the matrix, on the plane of the +45° fibres, was the main factor which influenced the fracture of the shaft.