Background: Personality factors are implicated in the vulnerability to adolescent alcohol misuse. This study examined whether providing personality-targeted interventions in early adolescence can delay drinking and binge drinking in high-risk youth. Methods: A randomised control trial was carried out with 368 adolescents recruited from years 9 and 10 (median age 14) with personality risk factors for substance misuse. Participants received either a personality-targeted intervention or no intervention. Outcome data were collected on alcohol use through self-reports at 6- and 12-month post intervention and analyses were conducted on the full intent to treat sample. Results: Multi-group analysis of a latent growth curve model showed a group difference in the growth of alcohol use between baseline and 6-months follow-up, with the control group showing a greater increase in drinking than the intervention group for this period. Interventions were particularly effective in preventing the growth of binge drinking in those students with a sensation seeking (SS) personality. SS drinkers in the intervention group were 45% and 50% less likely to binge drink at 6 (OR = 0.45) and 12 months (OR = 0.50) respectively, than SS drinkers in the control group, p = 0.001, phi = 0.49, Number Needed to Treat = 2.0. Conclusions: Considering the robust, inverse relationship between age of onset of alcohol use and later alcohol dependence, this intervention strategy may prove effective in preventing the onset of adult alcohol use disorders, by helping high-risk youth delay the growth of their drinking to a later developmental stage.