BACKGROUND: Emotion dysregulation (ED) is a common clinical feature of attention-deficit/hyperactivity disorder (ADHD). The present study examined the role of cognitive reappraisal (CR) and expressive suppression (ES) in adults with ADHD. In addition, resting-state fMRI (rs-fMRI) data were analyzed to identify neural substrates of CR/ES-ED relationships. METHODS: A total of 309 adults with ADHD and 163 healthy controls were recruited. ED was assessed using the 'emotional control' (EC) subscale from Behavior Rating Inventory of Executive Function-Adult Version. The Emotion Regulation Questionnaire was used to measure CR and ES. The functional connectivities (FCs) with the amygdala as Region of Interest, were analyzed in a subsample to explore their association with CR, ES and EC, respectively. RESULTS: Higher EC scores (indicative of lesser emotional control), as well as lower CR and higher ES utilization were detected in adults with ADHD compared with healthy controls. CR and ES were both negatively correlated with EC in adults with ADHD. Mediation analysis detected a potential effect of ADHD diagnosis on EC via CR. In addition, a unique significant mediation effect was found between ES-related FC of the right amygdala-prefrontal cortex and ED expression in adults with ADHD, confirming the '↑ES → ↓FCs [amygR-PFC] →↓EC' relationship. LIMITATIONS: Only self-reported scales and rs-fMRI data were included in these analyses. CONCLUSIONS: Our findings provide preliminary evidence that in adults with ADHD, less frequent use of CR accounts for ED expression, while more frequent use of ES may play a unique compensatory role in emotion regulation.