Introduction: The individuals with type 2 diabetes mellitus were supported with the individual motivational interview in the previous randomized controlled trial. The aim of this study was to assess whether the effect of motivational interview persists relative to the self-efficacy, metabolic control, and health-behavioral change of them. Methods: This study was contacted a cross-sectional design. This study was the follow-up to the previous randomized controlled trial. Total of 32 participants, including 18 from the intervention group and 14 from the control group, were contacted. No new intervention was performed to previous groups (control and intervention). The participants in the intervention and control groups were contacted by phone in the 18th month, and their self-efficacy, metabolic control and health behaviors were assessed. Results: The intergroup comparisons showed that the difference between the sixth month and 18th month was statistically significant except for medical treatment self-efficacy subscale score, postprandial blood glucose and waist circumference. The groups were similar in terms of their use of medicine, nutrition and physical activity behavior stages according to the 18th-month follow-up. Conclusion: This study found that the self-efficacy scores of the intervention group decreased negatively, and their metabolic values increased negatively in the 18th months, compared with the sixth month. In this respect, it is recommended that motivational interviews should be carried out at certain intervals assessing the characteristics of participants without discontinuing them after the intervention.