Concerns exist about availability and access to psychiatric services in the USA. For Medicare beneficiaries, one impediment to psychiatric services is the extent to which psychiatrists have opted out of the Medicare program.This study describes geographic variation in rates that psychiatrists opt out of Medicare, and assesses physician-level and geographic-level predictors of opt-out.Retrospective cross-sectional analysis of data describing psychiatrists' opt-out status as of March 2017 linked to data on psychiatrist location, psychiatrist characteristics (obtained from a comprehensive US physician database), and market area-level characteristics.27,838 psychiatrists in the USA MAIN MEASURES: Whether a psychiatrist had opted out of Medicare as of March 2017.Overall, 7.0% of psychiatrists (1940/27,838) opted out of Medicare as of March 2017. Opt-out rates varied substantially across states and within states. Physician-level factors independently associated with opt-out included: older age (psychiatrists > 65 years were 2.6 percentage points more likely to opt vs. psychiatrists < 35 years old, p = 0.03), greater years of experience, female gender (female psychiatrists were 2.6 percentage points more likely to opt out than male psychiatrists, p < 0.001), graduation from a top-20 ranked medical school (1.7 percentage points more likely to opt out of Medicare, p < 0.001), and domestic medical graduate (domestic graduates were 7.3 percentage points more likely to opt out of Medicare vs. foreign graduates, p < 0.001). Adjusting for other individual- and geographic-level factors, psychiatrists who practiced in areas with more psychiatrists per Medicare beneficiary were less likely to opt out (p < 0.001).The overall likelihood that psychiatrists opt out of Medicare is significant and varies considerably across regions and by characteristics of psychiatrists.