Numerical simulations of wave conditions in Callao bay in normal and extreme conditions were carried out to characterize the wave dynamics in the bay. Bathymetry data from the navigation charts to represent bottom depth were used. Waves in deep waters from numerical reanalysis were calibrated with satellite data that have allowed define scenarios of wave propagation to shallow water in normal and extreme conditions. Model results were compared with in situ wave data obtaining good approximation between modeling and observed waves. Results indicates that waves coming from Southwest and South-Southwest, which is the most predominant waves in deep waters, due to the diffraction effects caused by San Lorenzo Island generate two areas with different wave height conditions, in this way in the area affected by diffraction wave reach height between 0.5 to 1m, while area unaffected by diffraction effects wave reach heigh between 2 to 5m. Waves coming from Northwest has more influence in the bay, due to diffraction effects are neglected and in general terms all the bay increase the wave height around to 2 to 5m.