Due to a recent increase in environmental awareness regarding fish passage through hydraulic constructions including culverts, an evaluation for the passage of wild brown trout through a weir-baffled prototype-scale culvert was performed under a variety of culvert slopes and discharge conditions. The influence of the sample fish population and the length of the individual fish on passage rates were investigated; the data showed that the brown trout fish passage sample size evaluated in this study (25 per test) was sufficiently large to minimize sample size dependency. Fish behavior while traversing the culvert was observed and reported, including resting/staging zone locations. Turbulent flow through weir baffled-culvert was also simulated numerically using three-dimensional numerical model employing the (k- �) model, Renormalized Group k-� model (RNG), and Large Eddy Simulation (LES) model. Experimental data measured with the Particle Image Velocimetry (PIV) were used to assess the accuracy and the applicability of these turbulence models in predicting the turbulent flow characteristics of the flow through a weir-baffled culvert at different spatial locations inside the culvert for variety of culvert slopes and flow rates. The influence of flow rates and culvert slopes on the forward velocities and reverse velocities was evaluated. It was noted that the influence of the flow rates on the flow velocities depends on the culvert slopes. Turbulent kinetic energy and flow direction effects on flow characteristic were also evaluated. Validation of Manning’s equation and Manning’s roughness coefficient for the tested culvert were reported.