Abstract The study examined the effects of Substance Abuse on Maladaptive Behaviour and Academic Achievement among Secondary School Students in FCT, Abuja: Implications for Guidance. The study looked at substance abuse, causes of substance abuse, effects of substance abuse on maladaptive behaviour, effects of substance abuse on secondary school students, among others. The study concluded that schools can effectively address the effects of substance abuse on maladaptive behaviours and academic achievement with a holistic approach that involves early identification, education, behavioural counselling and collaboration with families and communities. The study therefore recommended that there should be comprehensive education and awareness programmmes on the dangers of substance abuse and the programme should be age-appropriate, interactive and designed to improve students’ understanding of the impact of substance abuse on behaviour, academic success and future opportunities, schools should offer accessible counselling services for students, collaborate with health services and law enforcement to address substance abuse issues, actively engage parents and the community in substance abuse prevention efforts by organising workshops, school should organise training workshop for their staff to recognise signs of substance abuse and maladaptive behaviours and respond appropriately, and schools should encourage students to participate in extracurricular activities that foster a sense of belonging, self-confidence and positive peer relationships. Such involvement can act as a protective factor against substance abuse by providing students with constructive outlets for their energy and emotions. Keywords: Substance Abuse, Maladaptive Behaviours, Academic Achievement and Guidance