Aims: The clinical relevance of diabetes-distress is increasingly recognized, but little is known about the efficacy of interventions specifically targeted to treat elevated diabetes-distress. Therefore, this systematic review sought to determine the efficacy of psychological interventions aimed at treating elevated diabetes-distress in people with Type 1 or Type 2 diabetes. Methods: We systematically searched literature from five databases. Randomized controlled trials (RCTs) with an English abstract, describing the results of a psychological intervention in adults with diabetes were included. Articles were eligible for inclusion if the primary outcome was diabetes-distress measured by the Problem Areas in Diabetes Scale (PAID-5/PAID-20) or the Diabetes Distress Scale (DDS-17). Only mean group diabetes-distress values above cut-off at baseline or the results of a subgroup above cut-off (PAID-5 ≥ 8, PAID-20 ≥ 40 or DDS-17 ≥ 3) were included. Results: The search yielded 8907 articles. After removing 2800 duplicates, 6107 articles remained. Titles and abstracts were screened, leaving 394 potential articles of interest, nine of which were RCTs. In a random-effects meta-analysis, the pooled effect size for diabetes-distress was 0.48 (Cohen's d), Z = 3.91, P < 0.0001. Statistical heterogeneity was I² = 46.67% (confidence intervals 45.06% to 48.28%). Diabetes-tailored psychological interventions reduced HbA1c (Cohen's d = 0.57), whereas mindfulness-based interventions did not (Cohen's d = 0.11). Conclusions: This systematic review shows that specifically diabetes-tailored psychological interventions are effective in reducing elevated diabetes-distress and HbA1c. More rigorous studies are warranted to establish the full potential of these interventions. PROSPERO database registration ID: CRD42017075290.