The economic, social, and cultural changes in the modern world have made adolescents between the ages of 12 and 18 important influences on family purchasing decisions. No longer solely users of products and services, adolescents now influence purchasing decisions and have attracted the attention of marketers and researchers. The purpose of this study is to analyze changes in the influence of adolescents aged between 12 and 18 on family purchasing decisions depending on socio-economic and demographic factors. This study aims to determine whether changes occur regarding different product groups by establishing at which stage of the decision process adolescent influence predominates. To achieve this goal, a survey method was used as a data collection tool. Using the convenience sampling method, adolescents within the age range of 12 and 18 were interviewed in Mersin, Turkey. The research results indicate that the influence of adolescents on family purchasing decisions occurs at different stages and depends on the type of product to be purchased. The analysis further shows that adolescents' age, gender, and number of siblings, and the family's total income, the father's level of education, and the mother's employment status also affect adolescent influence on family purchasing decisions.