Numerical simulations were performed to study the effects of various geometric and process parameters on the mixing characteristics of model gases undergoing mixing in multijet mixers. The computational fluid dynamics model was validated with the available experimental results in a Tee mixer. Good agreement between the simulated and experimental results was obtained. It is found that the d/D, q/Q and jet number have very significant effects on mixing. For the same flow rate and jet number, there is an optimum d/D for which the mixing is fastest and the total pressure drop is low. As q/Q decreases, the optimum d/D reduces. It can also be observed that multijet mixers (n = 4 and 6) can yield both good mixing when q/Q was the same and d/D was selected at the optimal value, respectively. The four-jet mixer has a bigger optimum d/D than the six-jet mixer. The mixing condition of the six-jet mixer varied shapely than 4 jets with d/D. The results presented here are very useful for the preliminary design of the multijet mixer for low viscosity fluids.