Motivations for and positive attitudes toward physical activity (PA) developed during childhood are likely to be carried over to adulthood. The purpose of this study was to examine the relationship between three psychological needs satisfaction, motivational regulations in physical education (PE), and attitudes toward participation in leisure-time PA among upper elementary school students. One thousand and seventy-three students in grades 3-5 anonymously and voluntarily completed three measures, including Psychological Needs Satisfaction, Motivational Regulations, and Attitudes, which were modified from previous works and judged by a panel of experts to ensure the wording of each item was understandable for upper elementary school students. The data were analyzed with descriptive statistics, composite reliability coefficient, and multilevel confirmatory factor analysis methods. The results indicated that the composite reliability coefficients of the measures were above 0.60, ranging from 0.62 to 0.79. The results of structural equation model indicated that satisfactions of autonomy, competence, and relatedness were significantly instrumental to the enhancement of autonomous motivation in PE settings and attitudes toward PA participation. Elementary school students' having fun, obtaining benefits, and being with friends were all major motivational factors contributing to positive attitudes toward PA outside of school.