We examined the role of older siblings in protecting adolescents from engaging in unsafe sexual practices. Participants included 297 midwestern high school students who were approximately 17 years old and who responded to questionnaires assessing their attitudes toward sexual intercourse, self-efficacy for engaging in safe sex, and discussions with their older siblings and parents about sex. Results suggested that sibling discussions about safe sex, in conjunction with parental discussions, predicted better attitudes toward safe sexual practices for adolescents. Perceptions of sibling relationship quality were more closely associated with sibling discussions about safe sex than were older siblings’ general attitudes toward safer sexual intercourse. Thus, sibling relationship quality may serve a protective function by facilitating more frequent sibling discussions about safe sex.