BACKGROUND: Globally, substance abuse has been identified as a major public health issue. The aim of the study was to determine and compare the prevalence, pattern, and predictors of substance abuse among adolescents in public and private day secondary schools in Katsina State. METHODS: A cross-sectional comparative study was employed to investigate 1126 adolescents obtained through multistage sampling technique in selected public and private day secondary schools across geopolitical zones spanning both rural and urban LGAs in Katsina State. Data was collected over eight weeks with the aid of pretested interviewer-administered questionnaire and was analysed using IBM SPSS version 25. Ethical approval was obtained from Katsina State Ministry of Health. RESULTS: Overall, majority (25.1%) of respondents were 18 years of age (majority, 28% in public and 25.2% in private schools were 17 and 18 years of age respectively. Overall mean age of the study population was 16.98 ± 1.27 years (Public
16.97 ± 1.237 years and Private
16.99 ± 1.309 years). Overall, most of the respondents were in SS3 (44.1%), (Public
47.4% and Private
40.8%). Proportion of adolescents who ever used any substance at least once was 22.02% (7.99% public, 14.03% private). Factors independently associated with substance abuse were being in SS3 class (p = 0.022), coming from monogamous family (p = 0.014) and peer substance abuse (p = 0.017). The logistic regression model reveals that current users in SS3 class, from monogamous setting and whose peers abuse substances are 7 times more likely (aOR = 7.12), 5 times more likely (aOR = 5.4) and 20% more likely (aOR = 0.209) to be in private than in public schools, respectively. CONCLUSION: Prevalence of substance abuse was high. Major predictor was peer substance abuse. Consequently, the state Ministry of Education in collaboration with Ministry of Health and NDLEA should design a substance abuse prevention programme with a view to reducing the menace of substance abuse in the state.