The present work elucidates the design and performance analysis of a three-dimensional microchannel for its capability in mixing two different liquids. Present studies are based on cross-T micromixer in which obstacles are introduced in the form of three-dimensional curved ribs. The mixing efficiency, quantified by the mixing index (M), has been calculated for the present micromixer. Results are also compared with those having straight ribs and found an enhancement of about 15% in mixing efficiency for obstacles with curved surfaces. However, this superior mixing has been achieved with a lower pressure drop, which provides an added advantage not traditionally realized for passive micromixers. Moreover, extensive parametric studies are also conducted to understand the effect of several geometrical parameters that can influence the mixing which include the height of obstacles (h), number of modules (Nm), angle of inclination (θ) and size of the obstacles and also the inlet Re. However, there has been seen to have certain optimum values of some of the parameters for achieving maximum degree of mixing. The use of the curved ribs is found to provide superior mixing for a wide range of Re. © 2018 Institution of Chemical Engineers