This study systematically summarize existing literature focusing on the correlates of students' moderate-to-vigorous physical activity (MVPA) during elementary school physical education (PE). A systematic search was initiated to identify studies investigating the physical activity correlates in students during elementary PE. Two researchers independently screened the studies, assessed their methodological quality, and extracted relevant data. The correlates were synthesized and further assessed using the semiquantitative method. A total of 42 studies were included in the review. Out of 44 variables identified from these studies, 10 were consistently associated with MVPA. Gender (boys), PE activities (team games), PE context (fitness activities, game play, and skill practice), class location (outdoors)and perceived competence were consistently and positively associated with the MVPA of students in PE. Other variables, namely body mass index, larger class size, and PE activities (movement activities), were consistently and negatively related to MVPA. In conclusion, this study improves our understanding of the correlates of students' physical activity from the demographic, biological, instructional, physical environment, social support, and psychological perspectives. These variables should be focused on when designing new or improving current interventions.