Mortality of HIV/TB patients in Eastern Europe (EE) is high. Little is known about their causes of death (COD).To assess and compare mortality rates and COD in HIV/TB patients across EE and Western Europe and Argentina (WEA) in an international cohort study.Mortality rates and COD were analysed by time from TB diagnosis (<3/3-12/>12 months) in 1078 consecutive HIV-/TB patients. Factors associated with TB-related death were examined in multivariate Poisson regression analysis.347 patients died during 2625 PYFU. Mortality in EE was 3-9-fold higher than in WEA. TB was the main COD in EE in 80%, 66% and 61% of patients who died <3, 3-12, or >12 months after TB diagnosis, compared to 50%, 0% and 15% in the same time periods in WEA (p<0.0001). In multivariate analysis, follow-up in WEA (IRR 0.12 [95% CI 0.04-0.35]), standard TB-treatment (0.45 [0.20-0.99]) and antiretroviral therapy (0.32 [0.14-0.77]) were associated with reduced risk of TB-related death.Persistently higher mortality rates were observed in HIV/TB patients in EE, and TB was the dominant COD at any time during follow-up. This has important implications for HIV/TB programmes aiming to optimise management of HIV/TB patients and limit TB-associated mortality in this region.