Background Although research participation is essential for clinical investigation, few quantitative outcome measures exist to assess participants’ experiences. To address this, we developed and deployed a survey at 15 NIH-supported clinical research centers to assess participant-centered outcomes; we report responses from 4,961 participants. Methods Survey questions addressed core aspects of the research participants’ experience, including their overall rating, motivation, trust, and informed consent. We describe participant characteristics, responses to individual questions, and correlations among responses. Results Respondents broadly represented the research population in sex, race, and ethnicity. Seventy-three percent awarded top ratings to their overall research experience and 94% reported no pressure to enroll. Top ratings correlated with feeling treated with respect, listened to, and having access to the research team (R2=0.80 - 0.96). White participants trusted researchers (88%) than did non-white participants collectively (80%) (p<0.0001). Many participants felt fully prepared by the informed consent process (67%) and wanted to receive research results (72%). Conclusions Our survey demonstrates that a majority of participants at NIH-supported clinical research centers rate their research experience very positively and that participant-centered outcome measures identify actionable items for improvement of participant’s experiences, research protections, and the conduct of clinical investigation.