This paper describes the trial of a novel intervention, Supporting Policy In health with evidence from Research: an Intervention Trial (SPIRIT). It examines (1) the feasibility of delivering this kind of programme in practice; (2) its acceptability to participants; (3) the impact of the programme on the capacity of policy agencies to engage with research; and (4) the engagement with and use of research by policy agencies. SPIRIT was a multifaceted, highly tailored, stepped-wedge, cluster-randomised, trial involving six health policy agencies in Sydney, Australia. Agencies were randomly allocated to one of three start dates to receive the 1-year intervention programme. SPIRIT included audit, feedback and goal setting; a leadership programme; staff training; the opportunity to test systems to facilitate research use in policies; and exchange with researchers. Outcome measures were collected at each agency every 6 months for 30 months. Participation in SPIRIT was associated with significant increases in research use capacity at staff and agency levels. Staff reported increased confidence in research use skills, and agency leaders reported more extensive systems and structures in place to support research use. Self-report data suggested there was also an increase in tactical research use among agency staff. Given the relatively small numbers of participating agencies and the complexity of their contexts, findings suggest it is possible to effect change in the way policy agencies approach the use of research. This is supported by the responses on the other trial measures; while these were not statistically significant, on 18 of the 20 different measures used, the changes observed were consistent with the hypothesised intervention effect (that is, positive impacts). As an early test of an innovative approach, SPIRIT has demonstrated that it is possible to increase research engagement and use in policy agencies. While more work is needed to establish the replicability and generalisability of these findings, this trial suggests that building staff skills and organisational structures may be effective in increasing evidence use.