This study examined cross-national similarities in a developmental model linking early age of alcohol use onset to frequent drinking and heavy drinking and alcohol problems 1 and 2 years later in a binational sample of 13-year-old students from two states: Washington State, USA and Victoria, Australia (N = 1833). A range of individual, family, school, and peer influences was included in analyses to investigate their unique and shared contribution to development of early and more serious forms of alcohol use and harms from misuse. Data were collected annually over a 3-year period from ages 13 to 15. Analyses were conducted using multiple-group structural equation modeling. For both states, early use of alcohol predicted frequent drinking, which predicted alcohol problems. Family protective influences had neither direct effects on heavy drinking nor effects on alcohol harm in either state, whereas school protection directly reduced the risk of heavy drinking in both states. Exposure to antisocial peers and siblings predicted a higher likelihood of heavy drinking and alcohol harm for students in both Washington and Victoria. Implications for the prevention of adolescent alcohol problems are discussed.