Although larger trials with a more representative sample of schools are needed, the study suggests the potential for kiR as an effective approach for substance use prevention in Kenya. A convenience sample of primary schools in metropolitan Nairobi was randomized into an intervention or control group. Teachers in intervention schools were trained to deliver the kiR curriculum with fidelity. Students in seventh and eighth grades in the intervention and control schools (N = 533) completed pretest and posttest questionnaires assessing substance use behaviors, attitudes, and drug resistance strategies. Although many primary school students in Kenya report use of alcohol and other drugs, evidence-based prevention interventions for schools are generally unavailable. Globally, there are growing opportunities to conduct research that assesses whether efficacious interventions from elsewhere can be adopted for new settings and populations. This small pilot study implemented and evaluated a linguistically adapted version of the school-based keepin' it REAL (kiR) universal substance use prevention program from the United States in Kenyan primary schools to assess its effectiveness and estimate potential effect sizes. Relative to the control group, kiR students reported several desired changes in behaviors and attitudes: less recent alcohol use and heavy (binge) alcohol drinking, and continuing or increased adherence to certain anti-drug norms. There was partial evidence that kiR helped students rely less on conflictual drug resistance strategies, such as reacting to substance offers angrily or with violence. Effect sizes for these outcomes compare favorably to those obtained in other school-based prevention interventions.