Blended Interaction is interaction in physical environments including meeting rooms, design studios, or libraries, that are augmented with new UI technologies to blend the power of digital computing with natural work practices and collaboration styles. It combines the virtues of physical and digital artifacts so that desired properties of each are preserved and computing is integrated in a considered manner. Since rapid technological advances constantly challenge existing designs, we believe that HCI should move beyond creating new technologies, single applications, and novel interaction techniques towards an overarching unified vision and theory of Blended Interaction. Our workshop will bring together leading experts in cognitive theories and post-WIMP designs and technologies to create this unified view of Blended Interaction in a multidisciplinary approach.