Expectations for impacts from research create demand for effective knowledge exchange between academic and non-academic settings. This complex process may be facilitated by "knowledge intermediaries." Learning from evaluation can advance recognition of their diverse roles and enhance these interactive relationships connecting research, policymaking and practice. The elusive subtlety of many knowledge exchange processes, which require attitudinal and behavioural changes, add to the challenge of impact generation. We use evaluations of publicly funded research to capture insights into the processes and good practice. Appropriately sensitive evaluation of impact generation can tap into this growing reservoir of "tacit knowledge" among such knowledge intermediaries.