Adolescent substance use is a top national public health concern with approximately 50% of youth having tried an illicit substance by the end of high school. The transition to high school is a critical point for substance use initiation. Despite this fact, there is relatively limited research looking at factors that can protect students from substance use initiation during this transition. The present study examines the protective effect of parental factors on the substance use initiation of youth. Participants included 1554 participants (57% female) who were predominately White (80%). The results indicated that parental support and involvement reduced the likelihood of substance use initiation during the transition from eighth to ninth grade. More frequent conversations regarding parental disapproval about drugs, however, was associated with substance use initiation or maintenance of substance use across time. Findings contribute to our understanding of protective factors for substance use initiation.