The purpose of this study was to evaluate the influences of a structured after-school program on student physical activity for third- through fifth-grade students at five schools in southern Colorado. The study utilized a pretest-posttest intervention design in which six elementary schools in a low socioeconomic status school district in southern Colorado were recruited to implement a structured curriculum into their existing after-school physical activity program. Four observations at each school were taken approximately 6 weeks apart during the 2014-2015 academic year. Randomly selected students (n = 187) were measured for height and weight at each observation and wore accelerometers during after-school physical activity. Descriptive statistics and independent sample t tests were calculated for a comparison of physical activity before and after the implementation of the structured after-school program. Students wore accelerometers an average of 45.72 ± 10.28 min/session. Total physical activity increased significantly from 36.21 ± 6.41 to 41.14 ± 6.76 min/session (p < 0.001). Moderate physical activity increased significantly from 9.29 ± 3.84 to 12.10 ± 5.96 min/session (p < 0.001), whereas vigorous activity significantly decreased from 8.02 ± 4.39 to 5.54 ± 5.32 min/session (p < 0.001). Overall, implementing a structured after-school program may be beneficial in increasing total physical activity, though its role in improving physical activity intensity is questionable.