Control of the temperature distribution in an extruder is important in maintaining consistent quality of an extruded polymer product. Due to nonlinear viscous heat effects and strong interaction along the direction of polymer flow, however, commercially employed decentralized SISO PID control often shows limited performance. As a way to realize more accurate extruder temperature control, in this paper, we present a simplified linear model for the extruder which takes the interaction effects into account, and a decentralized SISO MPC algorithm with feedforward compensation of the interaction effects. Performance of the proposed technique has been illustrated through numerical simulations.