PURPOSE: Young people, not in formal employment or education, face exceedingly high levels of intimate partner violence (IPV). We evaluated whether Stepping Stones and Creating Futures, compared with a wait-list control, can reduce IPV and strengthen livelihoods. METHODS: A cluster randomized controlled trial with 34 clusters in urban informal settlements in eThekwini Municipality, South Africa. Participant inclusion criteria were aged 18-30 years, resident in the informal settlement, and not working or in education. A total of 676 women and 646 men were recruited from September 2015 to September 2016. At recruitment, participants were not blinded to study arm. Endline data were collected from March to October 2018 (24 months postenrollment). Analyses were by intention-to-treat and separate for men and women. No clusters withdrew; endline retention was 74.9% (n = 505) men and 80.6% (n = 545) women. RESULTS: At endline in the intervention arm, men's self-reported past year IPV perpetration was lower (physical IPV [adjusted odds ratio [aOR]: .71, 95% confidence interval [CI]: .51-.97], severe IPV [aOR: .70, 95% CI: .52-.94], and sexual IPV [aOR: .74, 95% CI: .54-1.03]). There was no difference in men's controlling behaviors (β = .06, 95% CI: -.51 to .63) or past month earnings (β = .21, 95% CI: -.42 to .83). For women, earnings were significantly higher in the intervention arm (β = .97, 95% CI: .43-1.51), but there were no differences for past year IPV experience (physical IPV [aOR: .92, 95% CI: .62-1.37]; sexual IPV [aOR: .90, 95% CI: .64-1.28], severe IPV [aOR: .93, 95% CI: .66-1.31]) or controlling behaviors (β = -.01, 95% CI: -.88 to .86). CONCLUSION: Stepping Stones and Creating Futures is effective in reducing men's self-reported perpetration of IPV and strengthening women's livelihoods, but not women's experiences of IPV. TRIAL REGISTRATION: NCT03022370. Registered January 13, 2017.