<p>This article intends to explore the entropy generation analysis of chemically reactive micropolar fluid flow through a vertically placed microchannel under the impact of a transverse magnetic field. The governing equations are formulated with an impact of microrotation, Joule heating, viscous dissipation and chemical reactions. The momentum, microrotation, energy and mass equations are transformed into a dimensionless form and then solved using the Optimal Homotopy Analysis Method (OHAM). It is observed that a rise in micropolarity reduces entropy generation and enhances thermal efficiency, while magnetic and radiative influences greatly affect velocity and temperature fields. Chemical reactions dominate mass transfer and irreversibility distributions. The unique aspect of this study is the simultaneous examination of multiple interrelated factors in micropolar fluid systems, which results in novel insights into flow control and entropy reduction strategies. The findings directly impact engineering applications such as chemical process technologies, microreactors and microfluidic cooling systems, whose effective functioning depends heavily on thermodynamic optimization.</p>