We examine auditors’ role in diffusing forecasting knowledge among their clients. We hypothesize that auditors share forecasting process knowledge and best practices across clients, which improves management forecast accuracy. We find that companies forecast more accurately when their auditors have greater exposure to forecasting knowledge through other clients, consistent with forecasting knowledge diffusion through auditors. This association between auditor forecasting knowledge and management forecast accuracy is greater when managers (a) face more dynamic difficult-to-forecast environments, (b) have less skill and resources, and (c) have fewer alternative forecasting information sources. However, auditor forecasting knowledge is not associated with audit quality or auditor independence concerns, consistent with auditors affecting management forecasting through a knowledge sharing process unrelated to governance. Our results persist through multiple robustness tests, including an instrumental variable regression and selection models. Our research indicates a novel source of valuable knowledge that clients obtain from auditor knowledge sharing which improves clients’ unaudited information environment.