This paper deals with the bubbling flow and coagulant dosage modeling in an innovative continuous cascade-type electrocoagulation (EC) reactor using iron plate electrodes. The reactor comprises seven iron plates. It is open to the atmosphere at the top to release the hydrogen bubbles produced at the cathode during the reduction of H2O. In this context, a two-phase flow model (H2OH2) was formulated. The H2OH2 flow was obtained by the solution of the Reynolds Averaged Navier-Stokes (RANS) equations for the continuous phase (H2O), which was coupled to the slip model for the dispersed phase (H2). Since H2 bubble formation co-occurs at the cathode as the aqueous solution passes through the continuous EC reactor, the two-phase flow and Laplace equations were solved simultaneously. The modeling of the ferric ion coming from the anodic dissolution was carried out by solving the diffusion-convection equation. The influence of the mean linear inflow velocity (2.63 ≤ u ≤ 2.56 cm s−1) and current density (4 ≤ j ≤ 8 mA cm−2) on the H2 dispersion and coagulant formation (Fe3+) was systematically examined. A comparison between simulated and experimental Fe3+ doses showed deviations < 4%. Excellent agreement between experimental and theoretical residence time distribution curves was obtained.