Background: Type 2 diabetes mellitus (T2DM) is a highly prevalent public health problem. Although there is strong evidence supporting the essential role of physical activity in the management of T2DM, the prescription of physical activity has limited success in promoting changes in behavior. The purpose of the present study was to evaluate the impact of phone call support, over the course of five weeks, as an incentive to promote walking in type 2 diabetic patients with poor glycemic control. Methods: A total of 54 type 2 diabetic patients with poor glycemic control (HbA 1C Hg ≥8%) were enrolled in a randomized controlled clinical trial that was conducted at an outpatient clinic. The intervention patients received one telephone call per week for 5 weeks to encourage activity in the form of walking. Control patients did not receive phone calls. The number of steps each subject took was recorded weekly using pedometers. Results: Intervention group there was a significant increase in the number of steps per week between the first and last week compared to the control group (P<0.001). The absolute risk reduction was 75%, and it was necessary to provide phone call support for only three patients to obtain an increase in the number of the steps between the first and the last week of the study (NNT=3.0). Conclusions: Our results suggest that the telephone call, a high cost-benefit approach, may be an efficient intervention for promoting physical activity improvement in type 2 diabetic patients with poor glycemic control.