This research purpose to study the internalized stigma of psychiatric patients and the relationship between age and duration of mental illness with level of Internalized stigma of 46 psychiatric patients who were treated in the outpatient department at a primary care in Kalasin province. The instrument consisted of Overview of psychiatric patients and a measure of Internalized Stigma of Mental Illness Scale (Thai Version). Cronbach's Alpha Coefficient was 0.88. Data were analyzed using descriptive statistics and measure the relationship with Pearson' s Correlation Coefficient. The research found that most of the respondents were male, the mean age was 46.65 years (SD = 15.16). Most completed primary education or lower, unemployment, marital status single. Most diagnosis was schizophrenia, there is a period of severe mental illness, average 89.22 years (SD = 94.35). Most psychiatric patients are perceived stigma within their own mind at Minimal to no internalized stigma (xˉ = 1.78, SD = 0.81). In perspective of relationship found that age and duration of severe mental illness were related to very low levels of internalized stigma of psychiatric patients (r = 0.224, r = 0.158), respectively, a significant statistic was 0.05. Should be educated to recognize the self-stigmatization of psychiatric patients who have treated in primary care increased.