Understanding the factors that contribute to an effective teacher has the potential to influence selection and preparation of pre-service teachers and may influence student outcomes. Prior research suggests arelationship between teacher characteristics (academic achievement, verbal ability, gender) and teacher effectiveness, however,these factors explain only a fraction of the overall variance in the effectiveness of teachers. Guided by the What Works Clearinghouse protocol for Teacher Training, Evaluation and Compensation, this study involving pre-service teachers (N=400) used teacher performance rankings resulting from classroom observations and explored factors that may contribute to varying levels of teacher performance. Pre-service teachers' prior teaching performance, personality characteristics and previous academic achievement were assessed as predictive factors of teacher performance. Results indicate that no significantrelationship was identified between personality traits and the outcome variableteaching performance in this study. However, previous teaching performance in addition to academic achievement scores emerged as significant predictors of teaching performance.