The influence of geometrical and design parameters of T-jets mixers on flow dynamics and mixing patterns is studied by means of two-dimensional computational fluid dynamics simulations, planar laser-induced fluorescence, and test chemical reactions. The ratios between injector width and mixing chamber width and between width and depth of the mixing chamber were evaluated as parameters. These ratios determine the flow regime in T-jets mixers: high values of injector/chamber width ratio favor mixing and high depth values also increase the flow dynamics and thus mixing. A strategy for scale-up of T-jets mixers is devised, based on increasing a noncritical dimension (depth) while keeping other dimensions small.