Powder injection molding consisting of four stages - feedstock preparation, injection, debinding and sintering - is a unique technique to produce small and complex metal or ceramic components in high quantity. One of the limitations of this method is the production of thick components, which arises from difficulties in de-binding stage. In this study, a novel method is presented to produce thick components with large sections by powder injection molding using preformed inserts in the injection stage. By using a wrought insert on which the feedstock is injected, the thickness of an injected section that needs to be debound, is decreased, while the whole thickness of the component is still large. The key point in this method is the amount of diffusion welding of the wrought insert and the injected feedstock to form an integrated component. 316L stainless steel has been used as material for both insert and feedstock. The effects of insert/component diameter ratio and the sintering atmosphere on diffusion welding have been studied. Finally, a defect-free thick component with a diameter of 20 mm is fabricated with a bonded area at the interface of the insert and injected section having shear strength up to 427 MPa.