The aim of this study was to adapt for Turkish and perform the validity and reliability studies of the Immunosuppressant Therapy Adherence Scale®(ITAS®) which is developed by Chisholm et al.(2005). This cross-sectional and methodological study included adult Turkish renal, liver, and heart transplant recipients. Data were collected using the Demographic and Clinical Characteristics Form and Turkish version of Immunosuppressant Therapy Adherence Scale®. Construct validity was tested using exploratory and confirmatory factor analyses. Convergent validity was tested by correlating Immunosuppressant Therapy Adherence Scale-Tr® to serum immunosuppressant therapy concentrations. Reliability was tested using Cronbach's alpha and item-to-total correlations. Fifty transplant recipients were included. Root mean squared error of approximation was 0.04, standardized root mean square residual was 0.06, comparative fit index was 0.94, and goodness of fit index was 0.92. Kaiser-Meyer-Olkin was 0.62 and Bartlett's test was 27.791 (p< 0.001). Factor loads ranged from 0.62 to 0.93. Eugene value higher than 1 was obtained and explained 73.63% of total variance. Correlation between Immunosuppressant Therapy Adherence Scale-Tr® and serum immunosuppressant therapy levels was 0.544 (p< 0.001). Cronbach's alpha was 0.65; item-to-total correlation coefficients ranged from 0.27 to 0.69. Immunosuppressant Therapy Adherence Scale-Tr® is a valid and reliable tool to evaluate immunosuppressant therapy adherence in Turkish organ transplant recipients.