introduction: diabetes mellitus is an growing national and international public health concern. the number of people affected by diabetes in world by 2030 will be 69% in developing countries. regular physical activity plays a key role in the management of type 2 diabetes melitus, particularly glycemic control. it has been recommended that peoples with type 2 diabetes participate in moderate-intensity physical activity for at least 150 min each week, over at least 3 nonconsecutive days. despite these guidelines,the majority of adults with type 2 diabetes in iran are not active enough to achive health benefits. the aim of this study was investigation the efficacy of theory-based behavior change intervention to increase and maintain physical activity in female diabetic patients in tehran, iran. material and methods: a randomized clinical trial design was selected to examine the efficacy of the educational plan. control group received “diabetes and exercise” booklet. case group received educational plane based on theory of planned behavior and goal setting and planning strategies in two face to face sessions and ten telephone calls, plus “diabetes and exercise” booklet. vo2max and hba1c indexes were used as program outcome. data were analyzed with using of lisrel 8.8 and spss 15 softwares. results: in all 126 patients were entered into the study (64 participants in case, and 64 participants in control group). the mean age of patients was 46.38 (11.42) years. this study showed a significant diffrence in moderat and high physical activity between case and control groups 3 and 6 month after intervention (p<0.05). also a significant difference was found in vo2max in case group. the hba1c mean decreased in case group in this study but not significant. conclusion: this study confirms that this theory-based behavior change intervention could help to promote and maintain physical activity in iranian diabetic females and improve clinical indexes. it seems that strict monitoring of the behavior for better understanding of the results in subsequent studies is essential. key words: diabetic females, regular physical activity, theory of planned behavior, goal setting and planning strategies, vo2max, hba1c, promotion, maintenance. material and methods: a randomized clinical trial design was selected to examine the efficacy of the educational plan. control group received “diabetes and exercise” booklet. case group received educational plane based on theory of planned behavior and goal setting and planning strategies in two face to face sessions and ten telephone calls, plus “diabetes and exercise” booklet. vo2max and hba1c indexes were used as program outcome. data were analyzed with using of lisrel 8.8 and spss 15 softwares. results: in all 126 patients were entered into the study (64 participants in case, and 64 participants in control group). the mean age of patients was 46.38 (11.42) years. this study showed a significant diffrence in moderat and high physical activity between case and control groups 3 and 6 month after intervention (p<0.05). also a significant difference was found in vo2max in case group. the hba1c mean decreased in case group in this study but not significant. conclusion: this study confirms that this theory-based behavior change intervention could help to promote and maintain physical activity in iranian diabetic females and improve clinical indexes. it seems that strict monitoring of the behavior for better understanding of the results in subsequent studies is essential. key words: diabetic females, regular physical activity, theory of planned behavior, goal setting and planning strategies, vo2max, hba1c, promotion, maintenance.