Introduction: Due to the high nonadherence rate to posttransplant regimen and medical indications among liver transplant recipients, systematic patient-centered interventions are needed to improve the medium- and long-term graft and patient survival outcomes. Objective: The aim of this study was to develop and test the psychometric properties of Liver Transplant Therapeutic Adherence Questionnaire. Design: A mixed-method instrument design was conducted in 3 phases: (1) initial item collection was generated by inductive content analysis on internationally available resources, (2) item screening was carried out by a 3-member committee and 25 domain experts including nurses and physicians aiming to establish content validity, and (3) data were collected from 247 liver transplant recipients in May 2016 for psychometric testing. Results: A total of 221 knowledge statements were extracted as potential adherence assessment items. The qualitative screening phase resulted in top 35 important items. The second screening phase was performed quantitatively by 25 experts (n = 14 nurses, n = 7 gastroenterologists and hepatologists, and n = 4 transplant surgeons). A total of 16 items were associated with statistically significant content validity ratio values (≥0.37) to be included in the final questionnaire. Exploratory factor analysis revealed a distinct 4-factor structure that was labeled as: daily activities (α =.93), immunization (α =.93), nutrition (α =.92), and major complications (α =.79). Discussion: Our results reveal evidence of acceptable reliability and validity for Liver Transplant Therapeutic Adherence Questionnaire. This instrument makes it possible to measure recipients’ therapeutic adherence in both domains of research and practice.