Numerical simulations are carried out to study twodimensional steady flow inside passive micromixers using modified Tesla structures. Passive micromixers are advantageous over active micromixers because of their low cost and they can be easily fabricated and integrated with on-chip microfluidic systems. In this study, the effect of Tesla structures on the mixing performance of a cross-T microchannel is examined. Mixing performance is analyzed with numerical simulations and mixing contours for the modified Tesla structures. The effect of various geometrical parameters of the Tesla structures, namely the distance (L₂) radius (R), and the number of modules (Nm) on the mixing efficiency and the pressure drop, is analyzed. The results show that mixing can be enhanced by increasing the number of modules (Nm) and reducing L₂ but at the expense of additional pressure drop and manufacturing difficulty. It is also observed that the mixing efficiency slightly increases with the radius upto 50 µm after which it decreases sharply.