The End TB Strategy mandates that no tuberculosis (TB)-affected households face catastrophic costs due to TB. However, evidence is limited to evaluate socioeconomic support to achieve this change in policy and practice. The objective of the present study was to investigate the economic effects of a TB-specific socioeconomic intervention. The setting was 32 shantytown communities in Peru. The participants were from households of consecutive TB patients throughout TB treatment administered by the national TB programme. The intervention consisted of social support through household visits and community meetings, and economic support through cash transfers conditional upon TB screening in household contacts, adhering to TB treatment/chemoprophylaxis and engaging with social support. Data were collected to assess TB-affected household costs. Patient interviews were conducted at treatment initiation and then monthly for 6 months. From February 2014 to June 2015, 312 households were recruited, of which 135 were randomised to receive the intervention. Cash transfer total value averaged US$173 (3.5% of TB-affected households' average annual income) and mitigated 20% of households' TB-related costs. Households randomised to receive the intervention were less likely to incur catastrophic costs (30% (95% CI 22–38%) versus 42% (95% CI 34–51%)). The mitigation impact was higher among poorer households. The TB-specific socioeconomic intervention reduced catastrophic costs and was accessible to poorer households. Socioeconomic support and mitigating catastrophic costs are integral to the End TB strategy, and our findings inform implementation of these new policies.