Background: Diabetic patients with depression are often inadequately treated within primary care. These comorbid conditions are associated with poor outcomes. The aim of this systematic review was to examine whether collaborative care can improve depression and diabetes outcomes in patients with both depression and diabetes. Methods: Medline, Embase, Cochrane library and PsyINFO were systematically searched to identify relevant publications. All randomized controlled trials of collaborative care for diabetic patients with depression of all ages who were reported by depression treatment response, depression remission, hemoglobin A1c (HbA1c) values, adherence to antidepressant medication and/or oral hypoglycemic agent were included. Two authors independently screened search results and extracted data from eligible studies. Dichotomous and continuous measures of outcomes were combined using risk ratios (RRs) and mean differences (MDs) with 95% confidence intervals (CIs) either by fixed or random-effects models. Results: Eight studies containing 2,238 patients met the inclusion criteria. Collaborative care showed a significant improvement in depression treatment response (RR = 1.33, 95% CI = 1.05-1.68), depression remission (adjusted RR = 1.53, 95% CI = 1.11-2.12), higher rates of adherence to antidepressant medication (RR = 1.79, 95% CI = 1.19-2.69) and oral hypoglycemic agent (RR = 2.18, 95% CI = 1.61-2.96), but indicated a non-significant reduction in HbA1c values (MD = -0.13, 95% CI = -0.46-0.19). Conclusions: Improving depression care in diabetic patients is very necessary and important. Comparing with usual care, collaborative care was associated with significantly better depressive outcomes and adherence in patients with depression and diabetes. These findings emphasize the implications for collaborative care of diabetic patients with depression in the future.