The role of nonlinear variation of density with temperature (NDT) and concentration (NDC) on the free convective flow of non-Darcy micropolar fluid over an inclined plate has been studied for the first time. In addition, the modified form of thermal slip and isothermal condition is utilized to address heat transfer phenomena in nuclear plants, textile drying, and heat exchangers, etc. The respective partial differential equations and boundary conditions are cast into a sequence of the ordinary differential equation by the local non-similarity technique. The remodeled equations are simplified numerically by applying a successive linearization method (SLM). A constructive investigation emphasizing the influence of the Biot number, inclination of angle, nonlinear convection parameters on the drag coefficient, couple stress, mass and heat transfer rates. The results of this qualitative analysis are displayed graphically and the physical significance of the pertinent parameters is discussed in detail.