Moffit’s Developmental Taxonomy (1993) suggests that antisocial behaviour will either be constrained to adolescence (adolescent limited) or persist from childhood throughout the life course (life-course persistent). However, it has been suggested that a third trajectory should be added to the taxonomy - that being, adult-onset antisocial behaviour. Despite this, adult-onset antisocial behaviour lacks empirical evidence and there is discrepancies about its existence (Mata & Van Dunlem, 2012). Using a cross-sectional survey design, the current study examined moral disengagement, emerging adulthood and age as predictors of antisocial behaviour. This was measured using the Subtypes of Antisocial Behaviour scale (STAB) (Burt & Donnellan, 2009), the Moral Disengagement Questionnaire (Detert et al., 2008) and the Inventory of the Dimensions of Emerging Adulthood (Reifman et al., 2007). Data were collected on 211 participants aged 18-77 and the study was conducted via an online survey. The results demonstrated that overall age, moral disengagement and emerging adulthood predicted antisocial behaviour in an adult population. 26-45 year olds had the highest levels of antisocial behaviour, whilst 18-25 year olds had the highest levels of moral disengagement and identified most with emerging adulthood themes. Lower levels of emerging adulthood functioning and moral disengagement were associated with lower levels of antisocial behaviour. These findings can, in part, be the first to suggest that adult antisocial behaviour may be associated with emerging adulthood and moral disengagement aiding development of existing theory.