Background. Poor posture is a common musculoskeletal concern in children and adolescents and may lead to spinal discomfort and long-term structural issues. While excess weight has been linked to altered sagittal alignment, the impact of sports participation on spinal posture remains unclear. This study aimed to investigate the associations between weight status, sports participation, and sagittal spinal alignment in a pediatric population. Methods. This cross-sectional study was conducted within the “Ferrari Formula Benessere” corporate wellness program and included 698 children aged 5 to 16 years. Sagittal Index (SI) was measured using a standardized plumb line technique. Body mass index (BMI) was calculated and classified according to the WHO growth standards. Sports participation was self-reported and grouped into five categories: sedentary, skill-based, power-based, mixed, and endurance sports. Results. Age was the only significant independent predictor of the SI (β = 2.45, p < 0.001), with older children exhibiting higher SI values. Although a weak correlation was observed between BMI and SI (Spearman’s r = 0.24, p < 0.001), BMI was not a significant predictor when controlling for age. No significant differences in the SI were found between active and non-active children. Among sport disciplines, the SI was lowest in power-based sports (56.7 ± 22.3 mm) and higher in endurance (62.7 ± 24.4 mm), mixed (64.5 ± 23.2 mm), skill-based (61.1 ± 22.0 mm), and non-sport (64.2 ± 24.0 mm) groups, although these differences did not reach statistical significance (ANOVA p = 0.224). Conclusions. Age appears to be the primary factor associated with sagittal spinal alignment in children, while BMI and general sports participation showed no independent effect. Although some differences emerged between sport types, these findings were not statistically significant and should be interpreted with caution. These findings underscore the need for sport-specific, longitudinal research using objective posture assessment methods.