Medicare enrollment increases provider visits among older adults; however, it remains unclear whether this increase is uniform across all types of providers. Using data from the 2014-21 Medical Expenditure Panel Surveys, we examined the effect of Medicare enrollment on office and outpatient visits across providers, using a regression discontinuity design. We found that Medicare enrollment at age sixty-five led to a 14 percent increase in visits to primary care providers and a 31 percent increase in visits to other providers, with the former more prominent among Medicare Advantage enrollees. In contrast, there was no change in visits to mental health care providers. Our study highlights the heterogenous effects of Medicare enrollment on health care use across different types of providers. Strengthening partnerships across providers, especially between primary care and mental health care providers, could be one way to improve mental health care use among new Medicare enrollees.