Simultaneous Composite Injection Molding (SCIM) is an important method for evaluating interfacial adhesion between two distinct polymers. SCIM was performed to combine Polyoxymethylene (POM) and Poly (lactic acid) (PLA). These two polymers are different in terms of chemical as well as crystalline structures but successful combination of POM and PLA is possible due to the presence of compatible functional groups in both components. The interfacial strength between POM and PLA phases is evaluated by performing tensile tests on the SCIM specimens. The interfacial strength is extremely high because of the diffusion of the PLA molecules into the POM phase, particularly POM spherulite. The adhesion between PLA and POM or even POM/PLA blends is shown to be stronger than the adhesion between PLA and itself.