Buyers and suppliers often have multiple business relationships with each other across different geographical and product markets, forming a potentially complex web of connections. What happens between the firms in one geographical or product market may influence their interactions in others. Prior research in strategic management has found that similar multimarket contact in horizontal relationships between competitors has important consequences for the firms’ use of market power. However, the consequences of multimarket contact in vertical buyer–supplier relationships remain unexplored. Building on resource‐advantage theory, this study proposes that multimarket contact between buyers and suppliers is linked to their respective propensity to use three types of mediated power in their relationships (i.e., reward, coercion, and legal legitimate) and that the effects of multimarket contact differ between buyers and suppliers. A vignette study with 143 purchasing managers and 137 business‐to‐business sales managers tests the developed hypotheses. The findings show that a higher level of multimarket contact encourages suppliers to use legal legitimate power to a greater extent and encourages buyers to use reward power to a greater extent but legal legitimate power to a lesser extent.