This conceptual paper introduces the logic of embeddedness as a new theoretical angle to the IS planning stream of research. Taking two levels of analysis into account, we examine the impact of socially embedded ties on strategic interorganizational system (IOS) planning. We propose that from a dyad perspective, embedded ties facilitate the planning process, and can significantly increase the number of identified systems and their potential strategic value. Yet, paradoxically, having solely embedded ties in a network can adversely impact planning effectiveness by increasing (a) the risks of being insulated from novel ideas, (b) the likelihood of a lock-in effect, and (c) the salience of isomorphic pressures. We argue that, from a network perspective, those firms that manage to exploit an integrated mix of both embedded and arm’s length ties are more likely to succeed in their IOS planning. This paper contributes to SISP theory by identifying new interorganizational-level antecedents of planning effectiveness. It provides guidelines that IS executives can use to improve the effectiveness of their planning activities and ultimately achieve superior IT-business alignment