This paper investigates the outcomes of a policy experiment, the NSF SBIR/IUCRC Membership Supplement, designed to promote the success of small high-tech entrepreneurial ventures by providing subsidized memberships in university-based cooperative research centers (IUCRCs). Data collected via semi-structured interviews with representatives of 61 Small Business Innovation Research (SBIR) firms indicated that SBIR firms who used the supplement to join an IUCRC reported multiple R&D benefits including research cost avoidance, research savings, and access to expensive equipment. A vast majority of SBIR firms also reported realizing or anticipated realizing commercial benefits (e.g., new investors, new products, and improvements to existing products). As suggested by social capital theory, SBIR firms reported that the policy mix experiment helped them make new connections with faculty and industry. Following our qualitative results, a structural equation model was applied to test the effect of social capital as an antecedent of SBIR firm R&D and commercialization outcomes. Results suggested that the SBIR firms who developed more social capital through interactions with faculty and industry members realized significantly more R&D and commercialization benefits. Further, commercialization benefits mediated the relationship between social capital and the SBIR firm’s perceived return on investment. Overall, this study demonstrates the feasibility of subjecting mixed policy interventions to evaluative scrutiny and provides evidence that such instruments can have substantive and positive effects on small high-tech entrepreneurial ventures. We discuss implications for social capital theory, policy mix initiatives and entrepreneurship policy.