Using the data from the Early Childhood Longitudinal Study, Kindergarten Class of 2010-11 (ECLS-K:2011), this paper proposes to theoretically redefine and empirically capture the concept of emotional capital as it applies to students, employing five components (engagement, school belonging, grit, peer social support, and life satisfaction). The study demonstrates the associations between students' demographic characteristics and emotional capital on one hand, and the relationships between emotional capital and student behavior, on the other. We found that higher SES students and girls possessed higher levels of emotional capital. Stronger feelings of engagement and school belonging were associated with reduced internalizing and externalizing behavior problems, and improved approaches to learning. Grit and peer social support were associated with reduced internalizing behavior problems and improved approaches to learning. Higher level of life satisfaction was associated with reduced externalizing behavior problems. We discuss the implications of these findings to educational policy and practice.