Emotions are as important as the trainings for athletes to show high performance. Optimism and pessimism are among the emotions that affect athlete performance. In this study, it is aimed to develop the Athletes Optimism and Pessimism Scale (AOPS). For this purpose, athletes who do individual (n=193) and team sports (n=218) were included in the study. A total of 411 athletes participated in the study consisting of two study groups.  Exploratory factor analysis (EFA), confirmatory factor analysis (CFA), and convergent and divergent validity analyses were used to examine the validity of the scale. Besides, item-total correlations, Cronbach's alpha coefficient, Spearman Brown, Guttman Split-Half and test-retest coefficients were calculated for reliability concerns. The results showed that the items appropriately clustered under the optimism and pessimism subscales by relevant validity and reliability criteria. Exploratory Factor Analysis, it was determined that the scale explained 57.77% of the total variance. The scale, which has a 5-point likert-type assessment, consists of 18 items. AOPS consists of two sub-dimensions. The Optimism factor, whose eigenvalue is 7.40, explains 41.15% of the total variance and consists of 9 items. Pessimism sub-factor, whose eigenvalue is 2.81, explains 15.62% of the total variance and consists of 9 items. These are optimism and pessimism sub-dimensions. While the first nine items constitute the optimism subscale, the last nine items (10., 11., 12., 13., 14., 15., 16., 17. ve 18.) cluster under the pessimism subscale. These sub-dimensions and items in these sub-dimensions were analyzed by Confirmatory Factor Analysis. According to confirmatory factor analysis, the result of standard adaptation indices is satisfied. In line with the internal consistency analysis and test-retest analysis conducted to test the reliability of AOPS, it was determined that the scale has a highly reliable and time-stable structure. In the study, it was determined that the Developing The Athlete Optimism And Pessimism Scale (AOPS) is a valid and reliable measurement tool. 

Athlete, optimism, pessimism, the athlete optimism and pessimism scale