The effect of stitch density (SD) on fatigue life, stiffness degradation and fatigue damage mechanisms in carbon/epoxy (T800SC/XNRH6813) stitched using Vectran thread is presented in this paper. Moderately stitched composite (SD=0.028/mm 2 ; ‘stitched 6×6’) and densely stitched composite (SD=0.111/mm 2 ; ‘stitched 3×3’) are tested and compared with composite without stitch thread (SD=0.0; ‘unstitched’). The experiments show that the fatigue life of stitched 3×3 is moderately better than that of unstitched and stitched 6×6. Stitched 3×3 pattern is also able to postpone the stiffness degradation onset. The improvement of fatigue properties and postponement of stiffness degradation onset in stitched 3×3 is primarily due to an effective impediment of edge-delamination. Quantification of damage at various cycles and stress levels shows that stitch density primarily affects the growth rate of delamination.