Intrinsic motivation (IM) is an important predictor of children's physical activity participation. The present 3-year longitudinal study examined changes in IM toward physical activity among a group of at-risk boys (N = 92) at a summer sports camp. Results showed the boys were intrinsically motivated in their first camp year, but their IM levels declined throughout 3 years of participation. This decline might be due to insufficient instructor support and repetitively scheduled activities at the camp. There were no ethnic differences in the initial IM mean scores or rates of IM change. Such homogeneity might be attributable to the boys' similar demographic characteristics. Future research should identify possible causes of declined IM for camp coordinators and instructors to better design and implement sports and physical activities to sustain the boys' IM.