Background: Disruptive mood dysregulation disorder (DMDD) is characterised by severe emotion regulation difficulties, particularly anger and irritability, in children. Despite the impact of attachment on emotional and behavioural regulation, the link between attachment style and DMDD is under-researched.Aim: This study investigated whether attachment style and parasympathetic regulation differentiate the response profiles to frustrating conditions between children diagnosed with DMDD and controls.Setting: Participants were assessed at schools in Johannesburg, Gauteng, South Africa.Methods: Thirty participants were divided into two matched groups (nDMDD = 15; nControl = 15) and assessed. Respiratory sinus arrhythmia (RSA) and heart period were measured during an Affective Posner Task, inducing frustration. Attachment style was assessed using the Attachment Style Classification Questionnaire for children. Parents of children with DMDD completed a social interaction problems questionnaire.Results: The DMDD group showed a higher prevalence of avoidant attachment style (p = 0.013) compared to controls. Both groups displayed adaptive vagal withdrawal and recovery during the task (p = 0.005; p = 0.021). Controls had significantly higher heart period throughout the assessment (game 1: p = 0.006; game 2: p = 0.013; game 3: p = 0.007). In the DMDD group, lower vagal tone during frustration correlated with more social interaction problems (p = 0.049).Conclusion: The study demonstrates a potential link between attachment style and altered physiological state in children with DMDD.Contribution: The findings provide insight into possible atypical vagal regulation of the heart and avoidant attachment styles in DMDD, highlighting potential therapeutic and intervention targets.