Background:Occupational health nurses in workplaces aim to offer evidence-based interventions to increase physical activity among employees to promote health. Mobile health (m-health) interventions have demonstrated effectiveness in increasing physical activity, and the application of m-health solutions in workplaces warrants investigation. We examined the effectiveness of a cell phone/smart device and web-based (m-health) intervention in motivating the employees at financial enterprise firms to increase physical activity.Methods:This study included employees from 16 banks (n = 194) who were randomly assigned to either (a) an experimental group (6 banks, n = 89), which received an intervention that integrated the Theory of Planned Behavior (TPB)-based tailored Short Message Service (SMS) with web-based knowledge or (b) a comparison group (10 banks, n = 105), which received web-based messages alone. Outcomes included psychosocial variables (attitude toward physical activity, normative beliefs, and control beliefs) and the level of physical activity. Data were collected at baseline, immediately after the intervention, and 3 months after the intervention.Findings:The level of physical activity significantly increased in the experimental group (p < .05). TPB variables such as perceived social norms (p < .01) and behavioral control (p < .05) also significantly improved in the experimental group. However, all the effects had a small size (=.05) and diminished in 12 weeks.Conclusions:In addition to internet-based information, the use of mobile phones/smart devices to encourage employees to exercise for 8 weeks effectively increased employees’ physical activity level. More research, specifically addressing workplace culture, is warranted to establish methods for sustaining healthy behaviors to increase physical activity.