Background and Objective: Immediate interventions are necessary to improve the self-care behaviors of diabetic patients. This study aimed to investigate the effect of diabetes self-care education through WhatsApp virtual messenger on the self-care behavior of diabetic patients. Materials and Methods: This semi-experimental study was conducted in Jiroft, Iran, in 2019, and included 96 patients with type 2 diabetes who met the inclusion criteria and were selected randomly and divided into intervention and control groups using simple random allocation (lottery). The educational content of self-care was sent to the intervention group by the researcher for 8 sessions of 60 minutes (2 sessions per week) through the WhatsApp virtual messenger. Summary of Diabetes Self Care Activities questionnaire was completed in two stages before and one month after the end of the intervention in both groups. The obtained data were analyzed in SPSS software (version 24) through descriptive (Mean±SD) and inferential statistics (ANCOVA). Results: Before and one month after the intervention, the overall score of self-care behaviors and the scores of such subscales as diet adherence, foot care, blood sugar control, and regular medication use, increased significantly in the intervention group (P<0.001); however, there was no significant change in the overall score of self-care behavior and its subscales in the control group (P>0.05). Conclusion: Implementation of the self-care education program through WhatsApp virtual messenger helps to improve the self-care behaviors of diabetes patients and can be used as an effective method in preventing the adverse consequences of diabetes.