Text messaging is a promising means of intervening on an array of health issues among varied populations, but little has been published about the development of such interventions. The authors describe the development and implementation of an interactive text messaging campaign for parents to support behavior change among children in a childhood obesity randomized controlled trial. The authors invited 160 parents to participate in a text messaging intervention that provided behavior change support in conjunction with health coaching phone calls and mailed materials on behavioral goals. Throughout the 1-year intervention, the authors sent 1-2 text messages per week. The first asked how the child did with a target behavior the day before; parents who replied received an immediate feedback message tailored to their response. The second included a tip about how to work toward a behavioral goal. Baseline surveys indicate that text messaging is a common means of communication for parents, and many are willing to use text messaging to support behavior change for their child. Results at 1 year indicate a high level of engagement with the text messaging intervention, with nearly two thirds responding to 75% or more of the questions they were sent by text.