A Lagrangian modeling approach, which combines the direct simulation Monte-Carlo (DSMC) method and a Reynolds-averaged Navier-Stokes model to account for inter-particle collisions and turbulence characteristics of the carrier fluid, respectively, is proposed. The wall-bounded turbulent particle-laden flows in which the experimental data are available are chosen as the test problems for demonstration. Results obtained with the deterministic method accounting for interparticle collisions are used as a basis for validating the proposed stochastic Lagrangian model. Good agreement between the predictions obtained separately with the deterministic and DSMC methods is achieved. The benefit of saving computational expenditure when using the DSMC method becomes more remarkable than the deterministic method as the number of particles loaded in the flow is increased. In addition, the study demonstrates that tau(P)/tau(C) is a proper parameter to monitor the role of inter-particle collisions in the physical processes of particle-laden flows.