The purpose was to determine the effects of a school-based pedometer intervention (SBPI) on daily accrued steps, academic performance, attendance, tardiness, and fitness performance in middle school students. Students from one, public middle school were assigned to a control (n = 46) or a 6-week SBPI (n = 46). Both groups recorded daily accrued pedometer steps. Grade point average (GPA), tardiness, absenteeism, and physical fitness scores were assessed. While baseline daily accrued step-counts were similar (p = NS), SBPI significantly increased daily accrued step-counts versus control (p < 0.05). During the study interval, academic performance increased in both groups, while SBPI had reduced tardiness (p < 0.05) and a tendency for reduced absenteeism (p = 0.06) postintervention. Shuttle and mile run performance decreased from pre- to postintervention in both groups. These data suggest that SBPI can increase physical activity levels and decrease tardiness in middle school students, without translating into short-term improvements in academic or physical fitness performance.