OBJECTIVE: To assess the potential benefit of a workplace physical activity program on daytime sleepiness. METHODS: A total of 685 participants of a 4-month workplace physical activity program were assessed for daytime sleepiness (Epworth Sleepiness Scale [ESS]) at baseline, 4 months (postprogram), and 12 months. Changes in ESS were analyzed using multilevel mixed linear regression. RESULTS: In the total population, no changes in ESS scores were observed; 0 to 4 months: -0.2 (95% CI: -0.5 to 0.0), 4 to 12 months: 0.1 (95% CI: -0.2 to 0.4). In participants with baseline excessive daytime sleepiness (ESS > 10, n = 109), ESS scores improved significantly by -2.2 (95% CI: -3.0 to -1.4) at 4 months, sustained at 12 months; and almost half no longer had excessive daytime sleepiness by end of program. CONCLUSIONS: This study suggests that for employees with excessive daytime sleepiness, short- and long-term improvement in daytime sleepiness may be an unforeseen benefit of workplace physical activity programs.