The purpose of this study was to develop the Youth Physical Activity Attitude Scale (YPAAS). Questions were developed using dual-component (affective-cognitive, positive-negative) beliefs framework. Content validity was established with expert panel review. Two samples of 4th-8th grade students (51% Female; 9-14 years) completed the YPAAS (sample 1, n= 3,188; sample 2n= 679). Exploratory and confirmatory factor analyses and structural equation modeling were used to examine the construct and criterion validity of the YPASS. Results indicated a 12-item measure with positive and negative attitude dimensions. Students in upper-grade levels reported stronger negative attitudes toward physical activity compared to students in lower grades. The YPASS produced invariant scores for boys and girls. Structural equation modeling revealed that positive attitudes related to both physical activity intentions and behaviors. Overall, scores from the YPAAS were shown to be valid and reliable for capturing youths' positive and negative attitudes toward physical activity.