Background: Narcotics are substances or drugs that are natural, synthetic, or semi-synthetic that cause unconsciousness, hallucinations, and excitability. Drugs abuse survey results in 2017 in 34 provinces in Indonesia show that there are 3,376,115 people who use drugs. Purpose: The purpose of writing this article was finding out the source of cadres’ self-efficacy in preventing drugs abuse in Surabaya’s high schools. Method: This research method was a descriptive study with a qualitative approach. The informants of this study were high school students who were still active as anti-drugs cadres. The criteria for informant inclusion in this study were all high school students who were peer educators or anti-drug ambassadors in high schools in the North Surabaya area. When the study was conducted in October 2018 to June 2019. The method of data collection was in-depth interviews. Results: The results of this study were the source of self-efficacy of anti-drugs abuse cadres based on experience, observations of other individuals, verbal persuasion, and emotional and psychological conditions. The experience of the cadres included being a peer counsellor in drugs prevention, having participated in anti-drug communities, and experiencing following anti-drugs socialization. Component of experience through observation of other people, cadres did not make observations on people who had the same ability, but observations were made to people around cadres who had been involved in drug abuse. Components of verbal persuasion in this study concluded that there are others who always support all decisions and situations experienced by cadres, namely social support from teachers, parents, and peers. The Emotional/Physiological States component, namely the cadres in carrying out their duties felt happy because they have many positive changes and did not experience anxiety or pressure, which made them have positive self-efficacy. Conclusion: Sources of self-efficacy of anti-drugs abuse cadres are based on past experiences, observations of other individuals, verbal persuasion, and emotional and physiological conditions.