Trauma‐informed care (TIC) is a systems‐focused philosophy of service delivery based upon principles of choice, collaboration, empowerment, safety and trustworthiness that recognizes the pervasive impact of trauma across the human experience. In a grassroots effort, one organization developed an innovative, trauma‐informed day program to meet the needs of individuals with intellectual and developmental disabilities (IDD) who were recently deinstitutionalized. The present study is intended to provide an initial conceptualization and preliminary assessment of TIC within IDD services in order to understand its impact among individuals and staff. The study sought to answer the following questions: Has the program's culture been stable over time? How have individuals’ behaviors changed over time? What have been the experiences of the program's staff members with TIC? Through a mixed methods design, secondary data analysis and semi structured staff interviews were used to assess the impact of TIC. Findings revealed an initial strong presence of choice, collaboration, empowerment, safety, and trustworthiness within the program's culture, with non significant changes at follow‐up. Significant reductions were noted in overall challenging behavior, aggression, and PRN medication usage; while non significant changes were noted in physical interventions with the exception of “other” interventions (i.e., least restrictive) which significantly increased. Three major categories emerged from the qualitative data (making a difference, recognizing progress and compromising factors), illuminating staff satisfaction with work experiences, individuals’ progress, and factors that challenged fidelity to TIC. The study provides a preliminary conceptualization and evidence for the efficacy of the integration of TIC into IDD services despite methodological limitations and concerns regarding the use of physical interventions. Directions for future research are presented.