The influence of non-uniform single and double slot suction/injection into unsteady mixed convective MHD flow, heat and mass transfer of a viscous incompressible electrically conducting fluid over a vertical cone in the presence of transverse magnetic field, heat generation/absorption and a first order chemical reaction is studied. The unsteadiness is caused by the time dependent free stream velocity varying arbitrarily with time. Non-similar solutions are obtained by solving the coupled non-linear partial differential equations using the quasi-linearization technique in combination with an implicit finite difference scheme. Numerical results are reported here to account the effects of non-uniform slot suction/injection, buoyancy, magnetic field, heat generation/absorption and a first order chemical reaction on skin friction, heat and mass transfer coefficients. Results indicate that the skin friction, heat and mass transfer coefficients increase with non-uniform slot suction but the effect of non-uniform slot injection is just the opposite. Also, the skin friction, heat and mass transfer coefficients, respectively, increases with the magnetic parameter, heat absorption and chemical reaction parameters. (C) 2014 Elsevier Ltd. All rights reserved.