As part of a 5-year study to develop and validate an instrument for measuring success in long-standing community-based participatory research (CBPR) partnerships, we utilized the Delphi method with a panel of 16 community and academic CBPR experts to assess face and content validity of the instrument's broad concepts of success and measurement items. In addition to incorporating quantitative and qualitative feedback from two online surveys, we included a 2-day face-to-face meeting with the Expert Panel to invite open discussion and diversity of opinion in line with the CBPR principles framing and guiding the study. The face-to-face meeting allowed experts to review the survey data (with maintained anonymity), convey their perspectives, and offer interpretations that were untapped in the online surveys. Using a CBPR approach facilitated a synergistic process that moved above and beyond the consensus achieved in the initial Delphi rounds, to enhance the Delphi technique and the development of items in the instrument.