This paper reports the dual solutions in the MHD flow of a Casson fluid over a porous shrinking surface. In this study, viscous dissipation and Newtonian heating boundary condition effects are investigated. The governing partial differential equations are transformed into dimensionless form by the similarity transformation and then numerically solved by the Runge–Kutta–Gill procedure together with the shooting method. The non-dimensional velocity, temperature are displayed graphically for different controlling parameters. Dual similarity solutions are obtained for dimensionless velocity and temperature profiles. It is observed that the thermal boundary layer thickness increases as the Newtonian heating parameter increases in the presence of magnetic field. © 2018 Informa UK Limited, trading as Taylor & Francis Group.