Interfaces play a key role in determining the mechanical properties and macro behaviors of multi-material structures. Composites can be developed with toughening mechanisms and modified failure regimes through tailoring the material-interface relationship. It can be difficult to fabricate architected materials with interfaces using additive manufacturing, as multi-material print systems are limited in printing structures with widely differing aspect ratios. We propose a method of 3D printing multi-material architected structures through co-extrusion of filaments and interfaces, where the interfaces are dynamically tunable with differing mechanical properties during print. Nacre-like composite structures can be printed in “brick-and-mortar” configurations with tailored failure behaviors. This opens the door to a variety of material types with varied properties that can be rapidly printed together to create mechanical metamaterials used in biomedical, aerospace, and other engineered structures.