Background: Multiple sclerosis adult day programs (MSADPs) offer life-enhancing services for individuals and informal caregivers affected by multiple sclerosis (MS), including medical care, rehabilitation therapies, nutrition therapy, cognitive training, tailored education, exercise programs, and social interaction. The purpose of this study was to examine the effects of MSADPs on health-related quality of life (HRQOL) and health care utilization of persons with MS and HRQOL and well-being of informal caregivers. Methods: Using a quasi-experimental design, outcomes between baseline and 1-year follow-up in persons with MS and informal caregivers who used MSADP services and a comparison group of similar persons with MS and caregivers who did not use MSADP services were compared. For persons with MS, outcomes included standardized measures of physical and mental HRQOL and health care utilization. For caregivers, outcomes included physical and mental HRQOL and well-being. Changes in outcomes between baseline and follow-up were examined using propensity score-weighted difference-in-differences regression analysis. Results: For persons with MS, MSADP use had a significant positive effect on 12-Item Short Form Health Survey physical component scores, although the difference was not clinically meaningful. Use of MSADPs did not have effects on any other outcomes for persons with MS or caregivers. Conclusions: Use of MSADPs did not show a clinically meaningful effect on HRQOL for persons with MS or informal caregivers. The MSADPs do not seem to offer sustained benefits to persons with MS or caregivers, but the possibility of initial short-term benefits cannot be ruled out.