Aquaculture has been the world’s fastest-growing food producing method and grown to become the second-largest export industry in Norway during the past 40 years. Usually, the high-value fish such as Atlantic Salmon (Salmo Salar) is raised in a multi-cage fish farm, where the flow interactions between fish cages exist. In this study, the interactions between fish cages are implemented into the numerical program, FhSim, to investigate its influences on the responses of a multi-cage fish farm. Tensions in anchor lines, drag force, and cultivation volume of each cage in a full-scale 4 × 2 multi-cage fish farms under different flow directions are analyzed numerically. The discrepancies of the responses based on three cases, i.e., (i) without any wake effects, (ii) with only cage-to-cage wake effect, and (iii) with all the wake effects, are compared and discussed. The results indicate that neglecting the wake effects will overestimate the total drag force of the eight cages up to 128% and underestimate the total cultivation volume of the eight cages as much as 42%. This study can provide suggestions on how to consider the wake effects during the design of the multiple-cage system.