Diabetes mellitus (DM) is a chronic disease requiring changes in the behaviour of the entire family. The responsibility for implementing doctor’s recommendations falls mainly upon the mother. The aim of this study is to assess the psychosocial functioning of mothers of children with DM compared to mothers of healthy children. The study involved 120 mothers: 60 with children with DM and 60 with healthy children. Data were collected using an original social-demographic questionnaire developed by the authors as well as Antonovsky’s Sense of Coherence Scale (SOC-29), Schwarzer and Schultz’s Berlin Social Support Scales (BSSS), Rosenberg’s Self-Esteem Scale (SES), and Zigmond and Snaith’s Hospital Anxiety and Depression Scale (HADS). The assessment scales were standardised and accredited by the Polish Psychological Association. The results suggest that DM in children has no effect on the psychosocial functioning of mothers regarding their self-esteem and sense of coherence. However, mothers of children with DM are well-prepared for living in a difficult situation. Social support offered to mothers of diabetic children helps them to maintain their psychosocial health.