Secrets are prominent in close relationships. Most research has examined people’s general tendencies to share secrets or single instances of secret-keeping or secret-sharing. These methods limit what we know about how keeping and sharing secrets across time in established close relationships is associated with important relationship characteristics. This research focused on the role that secret exchanges play in how people assess relational closeness and social utility (i.e., being a valuable social connection) in friendships. Across 10 weeks, participants (N = 126) reported bi-weekly on sharing and receiving personal and secondhand secrets (i.e., third-party secrets) with three friends. We found that sharing and receiving more personal secrets were robustly associated with higher closeness and social utility. The findings on secondhand secret-sharing were more complex, suggesting that receiving secondhand secrets from friends and sharing secondhand secrets with friends were differentially associated with closeness and social utility when comparing short-term versus cumulative effects. Results are discussed in terms of how secret-sharing behaviors are dynamically associated with close relationship qualities.