Beliefs about the malleability of intellectual ability-mindsets-shape achievement. Recent evidence suggests that even young children hold such mindsets; yet, no reliable and valid instruments exist for measuring individual differences in young childrens mindsets. Given the potential relevance of mindsets to childrens achievement-related behavior and learning, we developed and tested the psychometric properties of the Growth Mindset Scale for Children (GM-C). Among other psychometric properties, we assessed this instruments (a) factor structure, (b) measurement invariance, (c) internal consistency, (d) temporal stability (test-retest reliability), (e) concurrent validity, and (f) cross-cultural robustness in samples of US children (Study 1; N = 220; ages 4 through 6; 50% girls; 39% White) and South African children (Study 2; predominantly grades 4 and 5; N = 331; 54% girls; 100% non-White). The GM-C scale exhibited four factors, representing beliefs about the instability of low ability, the malleability of low ability, the instability of high ability, and the malleability of high ability. The GM-C scale also demonstrated invariance across age, acceptable internal consistency (αs between .70 to .90), and moderate temporal stability over approximately one month (rs between .38 to .72). Concurrent validity was supported by significant relations between childrens scores on the subscales about low ability and their goal orientations (Studies 1 and 2), challenge-seeking behavior, and achievement in math and English (Study 2). These findings suggest that the GM-C scale is a promising tool for measuring mindsets in young children. We offer practical recommendations for using this new scale and discuss theoretical implications.