To examine the impact of a co-created culturally sensitive diabetes self-management education and support (DSMES) intervention on the physical and mental health of immigrants with type 2 diabetes (T2D). Pre- and post-test among people with T2D whose primary language was Urdu, Arabic or Turkish (n = 97). Participants were offered a six-week intervention based on a person-centred approach using research-based dialogue tools to facilitate learning and reflection, which was developed in co-creation with immigrants and healthcare professionals. Data were collected at baseline, post-intervention and after 6 months and analysed using paired t-tests, Wilcoxon signed-rank tests, chi-square tests and regression models when appropriate. Several clinical outcomes were improved post-intervention, including HbA1c (P < 0.001), body fat percentage (P = 0.002), self-rated general health (P = 0.05), well-being (P = 0.004) and several self-management behaviours, e.g., physical activity (P < 0.001). Most outcomes remained improved after 6 months, but the effect on HbA1c was no longer statistically significant. Some outcomes were improved only at 6 months, including waist circumference (P < 0.001) and diabetes-related emotional distress (P < 0.001). Fatigue did not change. Attendance at more programme sessions was associated with better outcomes. The DSMES intervention developed in a co-creation process was highly effective in improving the health of immigrants with T2D.