Our aim in this study was to investigate the relationships between physical activity (PA), pain, and injury among children. Secondarily, we examined whether these relationships differed between children with normal versus excessive weight or obesity. This was a cross-sectional study of 102 children (57 girls) aged 8-12 years old. We assessed the prevalence of moderate and vigorous PA using accelerometry over a seven-day period. We examined the associations between moderate PA, vigorous PA, pain presence, and injury presence using generalized estimating equations with a logit link and binomial distribution. We adjusted the obtained models for potential confounders and explored the moderating effect of weight status. We found no association between moderate PA and pain, but time spent in vigorous PA was associated with pain. Neither moderate or vigorous PA were associated with injury, and there was no moderating effect of weight status in these relationships. In summary, we found that objectively measured vigorous PA is associated with pain among 8-12 year old children. While these results should be replicated in longitudinal studies, they suggest that an association between vigorous PA and pain should be considered when developing PA interventions for children.