This paper reports on the results of a research-practice partnership that included a U.S. university research team and a state-funded grants program that supports informal science education. The goal of the 2-year partnership was to develop an empirically-tested model for collaboration and capacity-building (CCB) in support of collective evaluation. The model was implemented with 23 informal science education (ISE) organizations across one U.S. state. A comparison of pre and post-surveys indicate that the goals of the CCB model were attained. Participants reported an (1) increased perception of a common agenda, (2) increased capacity for conducting evaluation, and (3) increased peer-peer engagement. Participants also highlighted ongoing barriers to collective evaluation and suggested specific supports to overcome these barriers. This collaborative capacity-building model, although tested with ISE providers, is generalizable to other collective evaluation efforts.