The aim of the present study was to develop an attitude scale to measure students' attitudes toward out-of-school learning activities (OoSLA). The study was conducted with two separate study groups consisting of a total of 620 students. Expert opinion was sought on the content validity and face validity of the scale. An Exploratory Factor Analysis (EFA) and a Confirmatory Factor Analysis (CFA) were performed for the construct validity of the scale. The EFA yielded a structure consisting of 22 items and three factors, which accounted for 43.30% of the variance. The factors that were revealed were labeled as follows: "Avoidance of Activities and Deviating from the Learning Goal," "Motivation and Participation," and "Approaching the Learning Goal." The results of the CFA demonstrated that the scale had indices indicating an "acceptable fit" or a "perfect fit." The reliability of the measurements was examined by means of Cronbach Alpha, composite reliability, and the Spearman-Brown Split-Half Test Reliability methods, and it was determined that the calculated reliability coefficients were within acceptable limits. The results of Tukey's Test for Non-Additivity indicated that the scale was not additive. The item-total correlation and the 27% bottom-top group comparisons showed that all of the items on the scale were discriminatory. Ultimately, a valid and reliable measurement scale to reveal students' attitudes towards OoSLA was developed.