The positive impacts of physical activity (PA) on children's health and overall well-being are widely recognized. Nevertheless, a significant number of children fail to achieve the recommended PA levels, heightening their susceptibility to overweight, obesity, and non-communicable diseases. Features of the home and neighborhood environments may limit opportunities for children to participate in PA, yet context-specific evidence is required to develop targeted interventions in underrepresented low-income settings. This research examined the links between parents' perceptions of home and neighborhood built environment factors and moderate-to-vigorous physical activity (MVPA) in children residing in Kampala, Uganda. This cross-sectional investigation involved 256 children (55.5% female) aged 10–12 years and their parents/guardians. Children's MVPA was objectively assessed via waist-mounted ActiGraph accelerometers. Parental views of the environments were captured through a validated self-report questionnaire. Associations between environmental factors and children's MVPA were evaluated using linear regression models adjusted for clustering with robust standard errors. Gender-specific associations were explored through stratified analyses. Key findings included associations with play equipment availability at home (β = -2.37, p < 0.001; contrary to expected positive direction), residential density (β = 2.70, p < 0.05), and perceived crime safety (β = -5.29, p < 0.05; unexpected negative direction). Gender-stratified results showed varied and inconsistent patterns: greater perceived land-use mix diversity was linked to lower MVPA in girls (regardless of school type), while better sidewalk infrastructure (β = -12.01, p < 0.05) and walking/cycling facilities (β = -14.72, p < 0.05) correlated with reduced MVPA among girls in public schools. Higher perceived crime safety was associated with lower MVPA in both boys and girls attending private schools (β = -3.80, p < 0.05). Only a limited number of environmental attributes were linked to children's MVPA in this Ugandan context, with results often showing inconsistencies, particularly for girls. Additional research is essential to better comprehend the socio-ecological influences on health-promoting PA patterns among Ugandan children.
