In this study, the results of a parametric analysis of the entropy generation of mixed convection in a vertical parallel plate microchannel with asymmetric wall heat flux are presented. The fluid flow was assumed as Newtonian and fully developed. Analytical equations were derived to estimate the entropy generation and a specific MATLAB code was created to solve the governing equations. The effects of the modified mixed convection parameter (Gr(q)/Re), the Brinkman number (Br), the Knudsen number (Kn), and the ratio of wall heat flux (r(q)) on the entropy generation are presented and discussed. The results revealed that, while increment of Kn reduces the entropy generation, conversely, increment of Br/tau enhaces it. For each condition analysed, the entropy generation number related to heat transfer (N-R) is smaller than the entropy generation number related to fluid friction (N-F), indicating that N-F is dominant on the total entropy generation number (N-S).