This study examined whether implementing a whole health care model in a community mental health center reduced the use of acute care services and total Medicare expenditures. The whole health care model embedded monitoring of overall health and wellness education within the center’s outpatient mental and substance use disorder treatment services, and it improved care coordination with primary care providers. This study used fee-for-service Medicare administrative claims and enrollment data for June 2009 through July 2015 for the intervention (N=846) and matched comparison group (N=2,643) to estimate a difference-in-differences model. For the first two-and-a-half years of the program, Medicare expenditures decreased by $266 per month on average for each enrolled beneficiary in the intervention group relative to the comparison group (p<.01). Intervention clients had .02 fewer hospitalizations, .03 fewer emergency department (ED) visits, and .13 fewer office visits per month relative to the comparison group (p<.05 for all estimates). Overall, the whole health model reduced Medicare expenditures, ED visits, and hospitalization rates. These results may be due in part to the availability of more comprehensive medical data and staff’s improved awareness of client’s overall health needs. There was a lag between initial program implementation and the program’s substantial impact on health expenditures. This lag may be attributed to the substantial transformation and time needed for staff to adapt to the program.