Rationale: Impulsivity is a multidimensional construct that can predispose to psychopathology. Meta-analysis demonstrates an association between response impulsivity and Juvenile Myoclonic Epilepsy (JME), a common genetic generalized epilepsy. Here, we test the hypotheses that trait impulsivity is (i) elevated in JME compared to controls; (ii) moderated by specific seizure characteristics; and (iii) associated with psychiatric adverse effects of antiepileptic drugs (AEDs). Methods: Three hundred twenty-two participants with JME and 126 age and sex-matched controls completed the Barratt’s Impulsiveness Scale (BIS-brief) alongside information on seizure history and AED use. We compared group BIS-brief scores and assessed associations of JME BIS-brief scores with seizure characteristics and AED adverse effects. Results: The mean BIS-brief score in JME was 18.1±4.4 compared with 16.2±4.1 in controls (p=0.0007). Elevated impulsivity was associated with male sex (p=0.027), frequent absence seizures (p=0.0004), and lack of morning predominance of myoclonus (p=0.008). High impulsivity significantly increased the odds of a psychiatric adverse event on levetiracetam (p=0.036), but not any other psychiatric or somatic adverse effects. Conclusions: Trait impulsivity is elevated in JME and comparable to scores in personality and neurotic disorders. Increased seizure frequency and absent circadian seizure pattern moderate BIS score, suggesting disruption of both cortico-striatal and thalamocortical networks as a shared mechanism between seizures and impulsivity in JME. These findings warrant consideration of impulsivity as a distinct target of intervention, and as a stratifying factor for AED treatment in JME, and perhaps other types of epilepsy. The role of impulsivity in treatment adherence and psychosocial outcome requires further investigation. Funding: Please list any funding that was received in support of this abstract.: Canadian Institutes of Health Research; European Union Program of the Seventh Framework; UK Medical Research Council; Waterloo Foundation; the Charles Sykes Epilepsy Research Trust; NIHR, Biomedical Research Centre at South London and Maudsley NHS Foundation Trust; UK Engineering and Physical Sciences Research Council; DINOGMI Department of Excellence of MIUR 2018-2022; Health and Care Research Wales; Biomarin srl; ENECTA srl; GW Pharmaceuticals; Kolfarma srl; Eisai; South-Eastern Regional Health Authority; The Research Council of Norway; Epilepsy Research UK; Health & Care Research Wales; Wales Gene Park; Abertawe Bro Morgannwg University NHS R&D; UCB; Nationwide Children’s Hospital; Odense University Hospital; University of Southern Denmark.