ObjectiveThe DiaMind trial showed beneficial immediate effects of mindfulness-based cognitive therapy (MBCT) on emotional distress, but not on diabetes distress and HbA1c. The aim of the present report was to examine if the effects would be sustained after six month follow-up. Methods In the DiaMind trial, 139 outpatients with diabetes (type-I or type-II) and a lowered level of emotional well-being were randomized into MBCT (n = 70) or a waiting list with treatment as usual (TAU: n = 69). Primary outcomes were perceived stress, anxiety and depressive symptoms, and diabetes distress. Secondary outcomes were, among others, health status, and glycemic control (HbA1c). Results Compared to TAU, MBCT showed sustained reductions at follow-up in perceived stress (p < .001, d = .76), anxiety (p < .001, assessed by HADS d = .83; assessed by POMS d = .92), and HADS depressive symptoms (p = .004, d = .51), but not POMS depressive symptoms when using Bonferroni correction for multiple testing (p = .016, d = .48). No significant between-group effect was found on diabetes distress and HbA1c. Conclusion This study showed sustained benefits of MBCT six months after the intervention on emotional distress in people with diabetes and a lowered level of emotional well-being.