This article aims to present the flow and heat transfer characteristics of a nanofluid past an elastic sheet having variable thickness in the presence of a magnetic field. Vanishing nanoparticle flux at the boundary has been taken into account for the passive control of nanoparticles. Two-phase model for the nanofluid has been considered. With the help of similarity transformations, the governing nonlinear partial differential equations are converted into nonlinear ordinary differential equations along with the appropriate boundary conditions. The reduced equations are then solved numerically. The effects of buoyancy parameter,magnetic parameter, Brownian motion, thermophoresis parameter etc. on velocity, temperature and nanoparticle volume fraction are presented graphically and analysed in detail. Velocity, temperature and nanoparticle volume fraction are decreasing functions of wall thickness parameter for decelerated flow. Due to increasing values of thermophoresis parameter, the rate of heat transfer at the surface reduces while with the increase in the Brownian motion parameter the mass transfer rate at the surface increases.