No study, best of our knowledge, has been conducted on assessing the validity and reliability of community attitudes toward the mentally ill (CAMI) inventory in Iran. The questionnaire was translated into Persian and then returned to English. Content validity ratio (CVR), content validity index (CVI), impact score (IS) to assess content validity, Cronbach’s alpha, and test–retest reliability was used to prove the internal and external reliabilities, respectively. The questionnaires were distributed to 130 people from different levels of society. Some were in contact with at least one patient with mental illness and some others had no connection. After 2 weeks, the questionnaires were resent to 50 participants to evaluate the reliability using the test–retest method. All questions had CVI (>0.79) and CVR (>0.49) except for three questions (Q 10, 24, and 30), which were excluded from the questionnaire. The questions were relevant, clear, simple, and valid. The IS was more than 1.5. The Cronbach’s alpha values of four subscales including authoritarianism, benevolence, social restrictiveness, and community mental health ideology were recorded as 0.61, 0.49, 0.64, and 0.76, respectively. The CAMI scale is a valid and sustainable tool over time to assess the negative attitude toward mental illness.