Background: HIV/AIDS disease has remained highly stigmatized all over the world even though the increasing accessibility of its treatment. This study was designed to adapt the HIV/AIDS Stigma Instrument (HASI) to the Iranian People Living with HIV/AIDS (PLWHA). Methods: Translation –back translation of the scale into Persian was done. Then, the validity and reliability of the instrument were evaluated. The validity of the translated scale was assessed in three ways: evaluating its linguistic validity, assessing its content validity by a panel of nine experts, and exploring its construct validity by factor analysis. The internal consistency of the translated scale was evaluated by Cronbach’s Alpha.Results: HASI showed a good Content Validity Index (CVI value >0.75) and Content Validity Ratio (CVR >0.78). The internal consistency of the instrument regarding the total score was α=0.89. The three stigma subscales that were dis-tancing and blaming (8 items, α=0.87), fear (3 items, α=0.82), and discrimination (5 items, α=0.83).Conclusion: This article reports the development and validation of a new measure of stigma, i.e. HIV/AIDS Stigma Instrument in PLWHA (HASI-P), and provides evidence to support its content validity and internal consistency.