Globally, activists and researchers have pointed to the contribution of harmful alcohol and substance use conditions to the occurrence and severity of intimate partner violence (IPV). There has been much debate over the relationship and whether it is truly causal. To date, there has been limited evidence about whether interventions to prevent harmful alcohol use and treat common mental health problems have an impact on IPV outcomes, and whether gender-transformative interventions that seek to prevent IPV can reduce harmful alcohol use and improve mental health. Available evidence on these associations has largely been from the global North. DFID’s What Works to Prevent Violence Against Women and Girls Global programme (What Works) has generated new evidence on these associations from evaluations of IPV prevention interventions in a range of settings in the global South, including peri-urban Zambia, rural Rwanda and Ghana, and urban informal settlements in South Africa, with promising findings for IPV prevention.