This study was conducted to develop a new scale for measuring teachers' attitude towards science fair. Teacher Attitude Scale towards Science Fair (TASSF) is an inventory made up of 19 items and five dimensions. The study included such stages as literature review, the preparation of the item pool and the reliability and validity analysis. First of all, the draft scale including 48 items was prepared depending on science fair studies and interviews of teachers reported in related literature. The draft version of the scale was applied to 275 teachers from the cities of Zonguldak and Isparta in Turkey. The results of the exploratory factor analysis revealed that the teachers' attitude scale towards science fair made up of five factors including such dimensions as contribution to students' development, educational importance, judgment, negative behaviour and mentorship. The final version of the TASSF included 19 items. The reliability coefficients were found to be 0.82, 0.84, 0.70, 0.76 and 0.66, respectively, and the explained variances were calculated as 15.14, 14.09, 7.83, 7.35 and 6.93, respectively. The total variance of TASSF was 51.37, and the Cronbach alpha coefficient was 0.77. The results of the study demonstrated that this new Teacher Attitude Scale towards Science Fair was a valid and reliable scale to measure teachers' science fair attitudes. (Contains 2 tables.)