The signed donor card is an important method to overcome the shortage of organs for transplantation. A valid and reliable scale is necessary to have with the development of interventions to increase the signed donor card. This study aimed to develop and psychometric testing of the Signed Donor Card (SDC) in an Islamic society. This methodological study was conducted in Hamadan city, Iran in 2018 on 600 employees of offices. A 46-item scale was developed. It was assessed by face, content, and construct validities. Reliability was examined using the calculation of the Cronbach's α and test-retest method. The SPSS software version 22 and Mplus version 7.4 were used for data analysis. Our scale demonstrated acceptable internal consistency (α = 0.58-0.93) and good test-retest reliability (ICC = 0.76). The fitness indices for the confirmatory factor analysis (CFA) indicated that the model fit was good. CFA revealed nine standalone components including attitude, subjective norms, intention, anticipated regret, descriptive norms, perceived control, knowledge, non-cognitive beliefs, and religious beliefs. Convergent validity and discriminant validity were established. This study provided evidence concerning the validity and reliability of SDC scale. It can be used for the development and implementation of effective interventions for increasing signed donor card with the consideration of contextual and cultural situations.