Diabetic patients in Indonesia have poor self-care practices. Illness belief might affect diabetes self-care practice in Indonesia. However, up to date, the illness belief of Indonesian diabetic patients toward self-care is still unclear, and whether illness belief and its domains are the predictors of diabetes self-care practice in Indonesia is still unknown. Therefore, this study aimed to assess the illness belief and to assess whether illness belief and its domains are the predictors of diabetes self-care in the Indonesian context. A cross-sectional study was conducted on 625 T2DM patients from public health centers in Purwokerto City, Indonesia. A Brief Illness Perception Questionnaire (BIPQ) and Summary Diabetes Self-Care activities (SDSCA) were used to assess illness beliefs and diabetes self-care behaviors respectively. A hierarchical multiple regression analysis was conducted to identify the predictors of diabetes self-care behaviors. The scores of IBPQ domains (i.e., consequences, timeline, personal control, treatment control, identity, concern, understanding, and emotional response) were 5.00 ± 2.65, 4.84 ± 2.59, 6.16 ± 1.92, 7.21 ± 1.97, 5.00 ± 2.07, 4.91 ± 2.61, 5.31 ± 2.01, and 4.64 ± 2.51, respectively. The regression analysis showed the predictors of diabetes self-care behaviors to be consequences (p< .05), personal controls (p< .05), and duration of DM (p< .05). This study provides evidence that two domains of illness beliefs are predictors of diabetes self-care behaviors in Indonesia. The domains are consequences and personal control. There is a need to design educational programs focusing on illness beliefs to improve diabetes self-care behaviors in Indonesia.