PROMISE—Promoting Readiness of Minors in Supplemental Security Income (SSI)—was a joint initiative of the U.S. Department of Education (ED), the Social Security Administration (SSA), the U.S. Department of Health and Human Services, and the U.S. Department of Labor to fund and evaluate programs to promote positive changes in the lives of youth who were receiving SSI and their families. Under cooperative agreements with ED, six entities across 11 states enrolled SSI youth ages 14 through 16 and implemented demonstration programs intended to (1) provide educational, vocational, and other services to youth and their families and (2) make better use of existing resources by improving service coordination among state and local agencies. Under contract to SSA, Mathematica Policy Research is evaluating how the programs were implemented and operated, their impacts on SSI payments and education and employment outcomes for youth and their families (using an experimental design under which we randomly assigned youth to treatment or control groups), and their cost-effectiveness. In this report, we present findings from the process analysis of the first three years of the implementation and operation of the New York State (NYS) PROMISE program. The findings are based on data collected through October 2017 via site visits to NYS PROMISE, telephone interviews with and social network surveys of program administrators and staff, and the management information system that the program’s staff used to record their efforts. The report describes how NYS PROMISE engaged with youth, the services the program provided to them and their families, and the collaborations the program fostered to support its efforts. It also highlights information about the experiences of control group youth that could have implications for the evaluation’s impact analysis.