Determining possible associated factors and the influencing pathways to hemoglobin A1C (HbA1C) levels and quality of life (QoL) will facilitate the development of effective interventions to improve the physical and psychosocial health of patients with type 2 diabetes mellitus (T2DM).To test a hypothesized model that addressed the pathways among personal characteristics, social support, diabetes distress, and self-care behaviors to HbA1C and QoL.A total of 382 adults with T2DM were recruited. Self-reported questionnaires and medical records were used to collect data regarding personal characteristics, diabetes distress, and social support at baseline. The self-care behaviors characters were collected 6 months later, as well as QoL and HbA1C levels 1 year later.The 12-month QoL directly affected 12-month HbA1C levels. The 6-month self-care behaviors directly affected 12-month QoL, and indirectly affected 12-month HbA1C levels through 12-month QoL. Baseline diabetes distress directly affected 12-month QoL. Moreover, baseline diabetes distress indirectly affected 12-month HbA1C levels through 12-month QoL. Baseline social support directly affected baseline diabetes distress and 6-month self-care behaviors. In addition, baseline social support indirectly affected 12-month QoL through baseline diabetes distress. Baseline social support also indirectly affected 12-month QoL through 6-month self-care behaviors.Enhancing QoL is important to improve HbA1C levels. Enhancing self-care behaviors is essential to improve subsequent HbA1C control and QoL. Reducing diabetes distress is crucial to improve subsequent QoL. Improving social support is suggested a favorable strategy to reduce diabetes distress and enhance subsequent self-care behaviors in patients with T2DM.