Background: Diabetes management self-efficacy (DMSE) positively affects diabetes self-care behaviors and can lead to better glycemic control and improved disease outcomes in diabetes patients. Objectives: This study aimed to evaluate DMSE level and its relationship with medication adherence, glycemic control, and diabetes complications among type 2 diabetes (T2D) patients. Methods: A cross-sectional study was carried out from November 2019 to January 2020 on T2D patients who attended the Diabetes Center of the Kerman University of Medical Sciences. Data were collected using two validated questionnaires including the diabetes management self-efficacy scale (DMSES) to evaluate DMSE level and the eight-item Morisky medication adherence scale (MMAS) to assess adherence to medication. The SPSS statistical software version 22 was employed for data analysis. Results: Of 440 T2D patients entering the study, 72% were female with a mean (SD) age of 59.60 (10.48). The mean (SD) DMSE score of the respondents was 5.76 (1.87). A significant negative correlation was observed between DMSE with HbA1c (r = -0.289, P < 0.0001) and also with FBS (r = -0.229, P < 0.0001), but there was a significant positive correlation between DMSE and adherence to medication (r = 0.208, P < 0.0001). FBS level (β = -0.252, P < 0.0001), number of visits by specialty or subspecialty physicians (β = -0.139, P = 0.002), medication adherence score (β = 0.165, P < 0.0001), neuropathy (β = 0.142, P = 0.002), marital status β = 0.125, P = 0.004), household income (β = -0.126, P = 0.004), and blood glucose checks at home (β = 0.109, P = 0.013) were considered predictors of DMSE score. Conclusions: Diabetes management self-efficacy is considered suboptimal among T2D patients. Patients with higher DMSE have better adherence to medication, better blood glucose control, lower risk of neuropathy, and fewer visits by specialty and subspecialty physicians.