Abstract Objective: Medical education and teaching skills are core competencies included in the generic curriculum for specialty training. To support the development of these skills, there is need for a validated instrument. This study aims to develop and test an instrument to measure the attributes of specialty trainees as effective teachers. Methods: The study was conducted in two phases. In first phase, the content of the instrument was generated from the literature and tested using the Delphi technique. In second phase, the instrument was field tested for validity and reliability using factor analysis and generalizability study. Feasibility was calculated by the time taken to complete the instrument. Acceptability and educational impact were determined by qualitative analysis of written feedback. Attributes of specialty trainees were assessed by clinical supervisors, peers, and students. Results: The Delphi study produced consensus on 15 statements which formed the basis of the instrument. In field study, a total of 415 instruments were completed. Factor analysis demonstrated a three-factor solution ('learning-teaching milieu', 'teaching skills', and 'learner-orientated'). A generalizability coefficient was 0.92. Mean time to complete the instrument was five minutes. Feedback indicated that it was an acceptable and useful method of assessment. Conclusion: This new instrument provides valid, reliable, feasible, and acceptable assessment of clinical teaching.