Interfacial shear strength plays an important role in determining the mechanical properties of a fiber-reinforced ceramic composites. In this study, the effect ofinterlayer thickness on mechanical properties of Nicalon-fiber-reinforced SiC composites fabricated via polymer solution infiltration/chemical vapor infiltration (PSI/CVI) was studied. It was found that the flexural strength and fracture toughness of the composites were increased with the interlayer thickness and showed maximum value at the interlayer thickness of 0.66${mu}{ extrm}{m}$. Typical flexural strength and fracture toughness of Nicalon-fiber-reinforced SiC composites with interlayer thickness of 0.66${mu}{ extrm}{m}$ were 391.7$pm$34.6MPa and 15.1$pm$1.8MPa.m1/2, respectively.