It has been suggested that gain-framed messages are more effective than loss-framed messages in promoting low-risk health behaviors such as physical activity. Because of a heightened health concern and possible medical complications, older adults with type 2 diabetes (T2D) may consider physical activity to be risky. This study examined whether a reverse message-framing effect would be found among older adults with T2D. The participants included 211 sedentary and older adults with T2D recruited from an outpatient clinic. The participants were randomly assigned to receive either gain-framed or loss-framed messages and wore an accelerometer to monitor their physical activity for 2 weeks. The participants who received loss-framed messages were more physically active than those who received gain-framed messages (β = 0.13, p = .033). This loss-frame advantage might be attributable to the heightened perceived risks among older outpatients with T2D and the temporarily activated prevention-focused orientation in a clinical setting.