Identifying the clustering and correlates of physical activity (PA) and sedentary behavior (SB) is very important for developing appropriate lifestyle interventions for children and adolescents. This systematic review (Prospero CRD42018094826) aimed to identify PA and SB cluster patterns and their correlates among boys and girls (0–19 years). The search was carried out in five electronic databases. Cluster characteristics were extracted in accordance with authors’ descriptions by two independent reviewers and a third resolved any disagreements. Seventeen studies met the inclusion criteria and the population age ranged from six to 18 years old. Nine, twelve, and ten cluster types were identified for mixed-sex samples, boys, and girls, respectively. While girls were in clusters characterized by “Low PA Low SB” and “Low PA High SB”, the majority of boys were in clusters defined by “High PA High SB” and “High PA Low SB”. Few associations were found between sociodemographic variables and all cluster types. Boys and girls in “High PA High SB” clusters had higher BMI and obesity in most of the tested associations. In contrast, those in the “High PA Low SB” clusters presented lower BMI, waist circumference, and overweight and obesity. Different cluster patterns of PA and SB were observed in boys and girls. However, in both sexes, a better adiposity profile was found among children and adolescents in “High PA Low SB” clusters. Our results suggest that it is not enough to increase PA to manage the adiposity correlates, it is also necessary to reduce SB in this population.