The effect of plasticity on interface crack initiation from a free edge and crack propagation in nano-components is investigated by a proposed nano-cantilever bend method using a specimen consisting of ductile Cu and brittle Si and by a modified four-point bend method. The plasticity of Cu is estimated from the cantilever deflection measured by in situ TEM. Confined plastic deformation occurs near the interface edge and the crack tip. The critical stresses are close to each other in the region of about 10 nm, suggesting that the interface fracture is governed by elastic-plastic stress on the order of 10 rim.