This process study, part of the Strengthening Relationship Education and Marriage Services (STREAMS) evaluation, shares insights into the development and implementation of MotherWise, an Office of Family Assistance (OFA) Healthy Marriage and Relationship Education (HMRE) grantee designed to serve low-income pregnant women and new mothers in Denver, Colorado. The study examines: (1) how MotherWise was developed and how programming was built around the Within My Reach curriculum; (2) how participants were identified, recruited, and enrolled into MotherWise; (3) procedures for hiring, training, and supervising frontline staff; (4) how and to what extent MotherWise program leaders maintained fidelity to Within My Reach and the MotherWise implementation plans; and (5) participants’ engagement with and responsiveness to the program. An impact evaluation will assess the effectiveness of MotherWise on a range of outcomes one year and two-and-a-half years after random assignment. To maximize its contributions to the evidence base and to inform future program and evaluation design, the STREAMS evaluation is examining the full range of populations served by HMRE programs, including adult individuals, adult couples, and youth in high schools.