The present research aimed to conceptualize the construct of Teacher Assessment Identity (TAI) by designing and validating a questionnaire in the Iranian EFL context. In so doing, a tentative scale with 96 items was piloted on 340 novice and experienced Iranian EFL teachers using Exploratory and Confirmatory Factor Analysis (EFA, CFA). The results of the analyses led to the removal of 33 items, leaving the questionnaire with 61 items on a five-point Likert scale. Moreover, the results revealed that the construct of TAI has 12 factors including assessment "knowledge", "beliefs", "attitudes", "skills and confidence", "practices", "use assurance", "feedback", "rubric/criteria", "consistency and consequence", "grading/scoring", "question-types", and "roles". Likewise, the convergent validity and reliability of the instrument to measure the construct of concern was statistically confirmed (p>0.05). The findings have various implications for EFL teachers, teacher trainers, course designers, and language researchers by raising their awareness of assessment identity and its underlying components.