AbstractThis study developed a situation‐specific instrument that measures assertiveness of adolescents. The Assertiveness Scale for Adolescents (ASA), which contains 33 items, was constructed using a multiple‐choice format with three response alternatives. Based on data from 682 elementary and secondary school students, adequate reliability and validity of the ASA were obtained when tested against several variables about which predictions could be made. Potential use of the instrument in clinical diagnosis and research was discus