Abstract The paper presents an analysis of heat and mass transfer in the mixing chamber (MC) of steam–water injectors. It is aimed at determination of two-phase flow parameters at the MC outlet. The steam condensation in MC is described by 0D two-fluid model that assumes mechanical and thermodynamic non-equilibrium between vapor and liquid phases. To close the model equations, empirical correlation for condensate mass fraction at the MC outlet is proposed. It is based on pressure and temperature measurements on MC walls in four laboratory-scale injectors. The injectors differed primarily by motive steam expansion ratio that resulted in a change of steam pressure, temperature and velocity at the MC inlet. The proposed correlation predicts the condensate mass fraction with accuracy of 20% for the investigated injectors. Average heat transfer coefficient (HTC) in MC of the four injectors is also calculated using experimental data and then compared with the predictions of the proposed model. It is found that HTC values are in the range of 200–700 kW/m2K, depending predominantly on vapor–liquid temperature difference at the MC inlet.