Importance: Compared with traditional Medicare (TM) fee-for-service plans, Medicare Advantage (MA) plans may provide more-efficient care for beneficiaries with Alzheimer disease and related dementias (ADRD) without compromising care quality. Objective: To determine differences in health care utilization, care satisfaction, and health status for MA and TM beneficiaries with and without ADRD. Design, Setting, and Participants: A cohort study was conducted of MA and TM beneficiaries with and without ADRD from all publicly available years of the Medicare Current Beneficiary Survey between 2010 and 2016. To address advantageous selection into MA plans, county-level MA enrollment rate was used as an instrument. Data were analyzed between July 2019 and December 2019. Exposures: Enrollment in MA. Main Outcomes and Measures: Self-reported health care utilization, care satisfaction, and health status. Results: The sample included 47 100 Medicare beneficiaries (25 900 women [54.9%]; mean [SD] age, 72.2 [11.4] years). Compared with TM beneficiaries with ADRD, MA beneficiaries with ADRD had lower utilization across the board, including a mean of -22.3 medical practitioner visits (95% CI, -24.9 to -19.8 medical practitioner visits), -2.3 outpatient hospital visits (95% CI, -3.6 to -1.1 outpatient hospital visits), -0.2 inpatient hospital admissions (95% CI, -0.3 to -0.1 inpatient hospital admissions), and -0.1 long-term care facility stays (95% CI, -0.2 to -0.1 long-term care facility stays). A similar trend was observed among beneficiaries without ADRD, but the difference was greater between MA and TM beneficiaries with ADRD than between MA and TM beneficiaries without ADRD (mean, -15.0 medical practitioner visits [95% CI, -18.7 to -11.3 medical practitioner visits], -1.7 outpatient hospital visits [95% CI, -3.0 to -0.3 outpatient hospital visits], and -0.1 inpatient hospital admissions [95% CI, -1.0 to 0.0 inpatient hospital admissions]). Overall, no or negligible differences were detected in care satisfaction and health status between MA and TM beneficiaries with and without ADRD. Conclusions and Relevance: Compared with TM beneficiaries, MA beneficiaries had lower health care utilization without compromising care satisfaction and health status. This difference was more pronounced among beneficiaries with ADRD. These findings suggest that MA plans may be delivering health care more efficiently than TM, especially for beneficiaries with ADRD.