Background: The National Institutes of Health (NIH) announced a revised, expanded definition of 'clinical trial' in 2014 to improve trial identification and administrative compliance. Some stakeholders voiced concerns that the policy added administrative burden potentially slowing research progress. Methods: This quasi-experimental study examined the difference-in-differences impact of the new NIH clinical trial definition policy on participant recruitment progress in grants funded by the National Institute of Mental Health (NIMH). Results: One hundred thirty-two funded clinical trial grants were identified. While more grants were identified as clinical trials under the revised definition, the difference-in-differences in recruitment progress before and after the policy change was not statistically significant. Conclusions: The revised NIH clinical trial definition had no clear effect on recruitment progress in newly identified NIMH-funded clinical trials as compared to traditionally identified clinical trials. Concerns that administrative delays and burden could impact study progress may be alleviated by these initial results.