In this article, mode I interlaminar fracture toughness (GIC) of Vectran-stitched laminated composite is determined experimentally and computa- tionally. Critical strain energy release rates are measured by performing double can- tilever beam test on composites stitched with Vectran as stitch fiber, and are found to increase with increasing stitch thread thickness and stitch density. It is also revealed that the relationship between GIC and stitch density or stitch thread volume fraction appears to be linear. Interlaminar tension test is conducted to identify important fracture behavior of a single Vectran stitch fiber thread. The finite-element (FE) model of the stitched composite incorporates the novel four-step stitch fracture pro- cess, namely, interfacial debonding, slack absorption, fiber breakage, and pullout friction. The FE predictions of load-displacement curves and critical mode I strain energy release rates show good agreement with the experimental results. The differ- ences in interdependent stitch mechanisms between moderately stitched and densely stitched composites are discussed.