Successful treatment of dental caries, periodontal diseases and diabetes requires persistent daily self-care. The aim of this study was to evaluate the perception of self-efficacy as a common behavioral factor determining oral health behavior, diabetes self-care, and actual health status. Cross-sectional data relating to 149 insulin-dependent diabetes mellitus (IDDM) patients were collected from patient records, and by clinical oral examination and a quantitative questionnaire. The study population was recruited from different locations, and the participation percentage was 80%. Self-efficacy scales associated with corresponding behaviors, and a dental self-efficacy scale also correlated with dental caries. Dental self-efficacy correlated with diabetes self-efficacy, diabetes adherence, and with HbA1c. Also, logistic regression analysis revealed that dental self-efficacy was related to diabetes adherence. Further, those diabetics reporting a high frequency of dental visiting had higher diabetes self-efficacy. As a conclusion, good dental self-efficacy has a positive influence on diabetes adherence. The results suggest that the perception of self-efficacy may be a common behavioral factor determining diabetes self-care and oral health behavior.