People with diabetes have a higher risk of emotional distress (anxiety, depression) than non-diabetic or healthy controls. Therefore, identification of factors that can decrease emotional distress is relevant. The aim of the present study was to examine (1) the association between facets of mindfulness and emotional distress; and (2) whether mindfulness might moderate the association between potential adverse conditions (stressful life events and comorbidity) and emotional distress. Analyses were conducted using cross-sectional data (Management and Impact for Long-term Empowerment and Success—Netherlands): 666 participants with diabetes (type 1 or type 2) completed measures of mindfulness (Five Facet Mindfulness Questionnaire-Short Form; FFMQ-SF), depressive symptoms (Patient Health Questionnaire; PHQ-9), and anxiety symptoms (General Anxiety Disorder assessment; GAD-7). Hierarchical multiple regression analyses showed significant associations between mindfulness facets (acting with awareness, non-judging, and non-reacting) and symptoms of anxiety and depression (β = −0.20 to −0.33, all p < 0.001). These mindfulness facets appeared to have a moderating effect on the association between stressful life events and depression and anxiety (all p < 0.01). However, the association between co-morbidity and emotional distress was largely not moderated by mindfulness. In conclusion, mindfulness is negatively related to both depression and anxiety symptoms in people with diabetes and shows promise as a potentially protective characteristic against the influence of stressful events on emotional well-being.