As part of a parent intervention to reduce heavy-drinking, college freshmen were assessed for their attitudes toward drinking and reasonable alternatives to drinking on the weekends, as well as cognitive variables underlying attitudinal variables. Intervention parents received a handbook the summer prior to college entrance with information about college drinking and best practices for parent-teen communication. Results revealed that the association between intervention condition and drinking outcomes was mediated by attitudes favorable to drinking and reasonable alternatives to drinking, as well as beliefs about alcohol related behavior. This parent program was shown to be efficacious for changing high-risk drinking in college. Findings are discussed regarding the further development of college drinking prevention programs involving parents.