["Canadian Journal of Administrative Sciences / Revue Canadienne des Sciences de l'Administration, Volume 43, Issue 3, September 2026. ", "\nABSTRACT\nDrawing on research about middle managers' work relationships and the emerging socio‐cognitive perspective on ambidexterity, we examine how different horizontal and vertical interpersonal processes among middle managers and between middle and top managers contribute to business unit ambidexterity. Our framework also proposes that the impact of middle managers' horizontal knowledge exchange on business unit ambidexterity is shaped by the qualities (i.e., integrative bargaining and cognitive flexibility) of their vertical interpersonal processes with top managers. Results reveal complementarity of integrative bargaining and horizontal knowledge exchange, whereas cognitive flexibility in middle managers collaboration with top managers reduces the positive effect of horizontal knowledge exchange on BU ambidexterity. Our results have implications for the joint involvement of middle and top managers in fostering ambidexterity in multi‐unit organizations. We discuss the complementarities of middle managers' horizontal and vertical interpersonal processes as well as substitution effects and the associated guidance for middle managers' prioritization of interpersonal processes.\n"]