In this paper, the nonlinear radiation, chemical reaction, and Soret/Dufour effects on magnetohydrodynamic (MHD) natural convection about a permeable horizontal circular cylinder in non-Darcy porous media with heat source/sink are numerically analyzed. The surface of the horizontal circular cylinder is subjected to uniform wall temperature and uniform wall concentration (UWT/UWC). The governing equations are transformed into dimensionless, non-similar forms using suitable non-dimensional variables and then solved using Keller box method (KBM). Comparisons with previously published work are performed, and the results are found to be in an excellent agreement. Numerical data of the dimensionless temperature profile, the dimensionless concentration profile, the Nusselt number, and the Sherwood number are presented in graphic and tabular forms for the main parameters. The physical aspects of the problem are discussed in detail. The Nusselt number increases with increasing the Soret parameter, radiation parameter, and surface temperature ratio. Increasing the Dufour parameter, radiation parameter, surface temperature ratio, coefficient of space-dependent internal heat generation/absorption, and dimensionless chemical reaction parameter enhances the Sherwood number.