Background : Globally, 382 million people are estimated to have diabetes. To date there is paucity of evidence regarding predictor of regular physical activity among Type 2 diabetes mellitus patients with application of Trans-theoretical model. Therefore the objective of this study was to determine predictors of regular physical activity among type 2 diabetes mellitus patients in Wolaita Sodo University hospital using the Trans- theoretical model. Method : Institutional based cross-sectional study was conducted on 400 systematic random selected Type 2 diabetes mellitus patients. One-way ANOVA was used to show mean scores differences of processes of change, decisional balance and self-efficacy across stages of change. Multivariable logistic regressions were also conducted. Result : Of the participants, 34.3% were physically active. The processes of change, the pros and the self-efficacy significantly increased from precontemplation to maintenance stage while the cons decreased across the stages (p<0.05). The result of multivariable logistic regression showed that pros, cons, self-efficacy, self-liberation and counter conditioning were predictors of physical activity. Conclusion : Type 2 diabetes mellitus patients’ physical activity was very low. Stage matched intervention should be designed to increase processes of change, pros and self-efficacy from precontemplation to maintenance stages. [Ethiop. J. Health Dev. 2018;32(2):97-103] Key words : Physical activity, Type 2 diabetes mellitus, Transtheoretical model