Background: It cannot be denied that many improvements in female and child health have been achieved worldwide through international family planning programs. More than half of the females (57%) with unintended pregnancy admitted that they had not used birth control the month before conception. Objectives: The aim of this study was to promote family planning practice among females of Zahedan (southeast of Iran) through the transtheoretical model (TTM). Patients and Methods: The current quasi-experimental study was conducted on 96 eligible females, who were allocated either to the case or the control group and were selected from homes in the border of Zahedan city (southeast of Iran) during 2010. Convenience sampling by door-to-door visits was used for finding eligible cases. ATTM-based self-administrated family planning questionnaire was used for data collection. Participants in the intervention group received education in two groups, based on their stage of change: precontemplation, contemplation, preparation, action, maintenance, and all groups were followed for three months. Results: The result of the chi-square test did not s how any significant difference in the stage of change: precontemplation, contemplation, preparation, action, maintenance before education between the control and intervention groups (P = 0.55). After education, subjects in the intervention group moved forward through stage of change and got at least one step closer to the family planning behavior., with this change being significant (P < 0.001), while the movement of participants through stage of change not being significant in control group (P = 1). The results of statistical tests illustrated that the mean knowledge of the intervention group was 7.5 +/- 7.1 versus 0.5 +/- 4 for the control group (P < 0.001), mean of attitude of the intervention group was 5.5 +/- 5.41 versus 0.09 +/- 2.04 for the control group (P < 0.001), and practicing family planning methods (P < 0.007) in the intervention group was higher than the control group after education based on TTM. Conclusions: According to this study the educational plan based on TTM was effective in changing knowledge, attitude, and practice and directing females towards taking action. Moreover, self-efficacy; perceived barriers and benefits are factors that affect the use of family planning methods.