Research Summary: This study contributes to the literature on strategic alliances by examining the impact of collaboration on competition between partners in product markets. We integrate the alliance learning and social network perspectives to examine how different combinations of exploratory and exploitative alliances between a firm and its partner influence the firm's competition against its partner in product markets. Using a longitudinal dataset collected in the U.S. pharmaceutical industry (1984-2003), we find an inverted U-shaped relationship between relative exploration (i.e., the proportion of exploratory alliances in the collaborative portfolio between a firm and its partner) and the firm's competition against its partner. This relationship is negatively moderated by firms' relational and structural embeddedness, but positively moderated by their positional embeddedness. Managerial Summary: This study examines how different combinations of exploratory and exploitative alliances between two firms affect their competition in the product market. Using a 20-year dataset collected in the U.S. pharmaceutical industry, we find that the proportion of exploratory alliances (i.e., joint development of critical innovations) in the alliance portfolio between a firm and its partner increases the firm's competition against its partner, up to a tipping point at which such competition starts to decline. Given a certain combination of the two types of alliances, such competition is stronger if the firm has more alternative allies than its partner but weaker if the firm and its partner have previously collaborated or share common allies in their networks.