Objective To compare physicians' self‐reported willingness to provide new patient appointments with the experience of research assistants posing as either a Medicaid beneficiary or privately insured person seeking a new patient appointment. Data Sources/Study Setting Survey administered to California physicians and telephone calls placed to a subsample of respondents. Study Design Cross‐sectional comparison. Data Collection/Extraction Methods All physicians whose California licenses were due for renewal in June or July 2013 were mailed a survey, which included questions about acceptance of new Medicaid and new privately insured patients. Subsequently, research assistants using a script called the practices of a stratified random sample of 209 primary care physician respondents in an attempt to obtain a new patient appointment. By design, half of the physicians selected for the telephone validation reported on the survey that they accepted new Medicaid patients and half indicated that they did not. Principal Findings The percentage of callers posing as Medicaid patients who could schedule new patient appointments was 18 percentage points lower than the percentage of physicians who self‐reported on the survey that they accept new Medicaid patients. Callers were also less likely to obtain appointments when they posed as patients with private insurance. Conclusions Physicians overestimate the extent to which their practices are accepting new patients, regardless of insurance status.