In this study, the effectiveness of the Observed Protective Behaviors behaviors test, a single-session, disclosure-focused, in situ skills training (IST), was evaluated as a standalone program (IST only) or as a booster to the child protective education program, Learn to be safe with Emmy and friends ™ (program + IST). Participants included 281 Year 1 children (5–7 years; 52% male), randomly assigned to IST only, program + IST, program only or waitlist, and followed across 6 months. At each assessment, children completed interviews to assess their intention and confidence to disclose unsafe situations (disclosure intentions and confidence) and their ability to identify unsafe situations (safety identification skills). Children also reported their anxiety symptoms to assess for a possible iatrogenic effect. The IST-only condition was effective, with children showing increased disclosure intentions relative to waitlist children. The program + IST condition was also effective, with children showing increased disclosure intentions relative to children in the waitlist or program-only conditions as well as greater increases in disclosure confidence relative to waitlist children. No differences were observed between conditions in children’s safety identification skills, and no iatrogenic effect on anxiety was found. Future research may seek to develop an IST that will also boost children’s safety identification skills.