This study examined the relationship between substance abuse and criminal behaviour among youth in Uganda, with Wakiso Municipality serving as the primary case study. The study was motivated by growing concerns about the escalating prevalence of substance use including alcohol, cannabis, tobacco, and prescription drug misuse among Ugandan urban youth and its documented association with increased criminal activity, public safety challenges, and socio-economic marginalisation. Drawing on a cross-sectional survey of 196 respondents including youth aged 15– 35, community leaders, law enforcement officers, and social workers, supplemented by key informant interviews and focus group discussions, the study employed descriptive statistics, chi-square association tests, Pearson correlation, and multiple linear regression to examine how alcohol abuse, illicit drug use, and prescription drug misuse influenced different categories of criminal activity among youth in Wakiso Municipality. Descriptive findings revealed high prevalence rates of multiple substance use categories, with 62.8% of youth respondents reporting current or recent alcohol use and 41.3% reporting cannabis use. Pearson's correlation confirmed significant positive relationships between all three substance abuse dimensions and youth criminality (r = 0.583 to 0.741, p < .001). Regression analysis demonstrated that substance abuse collectively explained 66.8% of the variance in youth criminal behaviour (R² = 0.668, F = 41.72, p < .001), with alcohol abuse emerging as the strongest predictor (β = 0.438, p < .001). The study concluded that substance abuse was a primary driver of youth crime in Wakiso Municipality and recommended comprehensive drug demand reduction programming, community-based rehabilitation services, and law enforcement capacity strengthening as integrated response priorities.