The transition of people from paediatric to adult diabetes services is associated with worsening glycaemia and increased diabetes-related hospitalisation. This study compared the clinical characteristics of those with and without mental health conditions among attenders at a diabetes young adult clinic diabetes before and after changes in service delivery. Retrospective review of 200 people with diabetes attending a Sydney public hospital over eight years corresponding to the period before (2012-2016) and after (2017-2018) restructuring of a clinic for young adults aged 16-25 years. Characteristics of those with and without mental health conditions (depression, anxiety, diabetes related distress, eating disorders), were compared. Among clinic attenders (type 1 diabetes n=184, 83.2%), 40.5% (n=89) had a mental health condition particularly, depression (n=57, 64%), which was higher among Indigenous than non-Indigenous people (5.6% vs 0.8% p=0.031) but similar between diabetes type. Over eight years, those with, compared with those without a mental health condition had higher HbA1c at the last visit (9.4%[79 mmol/mol] vs 8.7% [71 mmol/mol], p=0.027), the proportion with diabetic ketoacidosis (DKA 60.7% vs 42.7%,p=0.009), smoking (38.4 vs 13.6%,p=0.009), retinopathy (9.0 vs 2.3%,p=0.025), multiple DKAs (28.4 vs 16.0%,p=0.031) were significantly higher. Having a mental health condition was associated with 2.02 (95% Confidence intervals 1.1-3.7) fold increased risk of HbA1c ≥ 9.0%[75mmol/mol]. Changes to the clinic were not associated with improvements in mental health condition (39.0% vs 32.4%, p=0.096). In conclusion, we found that mental health conditions, particularly depression, are common in this population and are associated with diabetes complications. Diabetes type and clinic changes did not affect the reported mental health conditions. Additional strategies are required to reduce complication risks among those with mental health conditions. .