Manipulation of particles suspended in fluids flowing in microfluidic channels is required in a variety of biological, diagnostic and therapeutic applications. For instance, alignment of particles into a tight stream is a necessary step prior to their counting, detecting, and sorting. Generally, this task is accomplished by using a Newtonian fluid as suspending medium and by properly fabricating a complex device aimed to displace particle trajectories. In the last years, however, the use of polymeric liquids in microfluidic processes has received a growing interest. Indeed, the addition of a small amount of polymer in a Newtonian suspension flowing in a channel promotes “internal” forces that can be exploited to manipulate the trajectories of suspended particles in simple devices. In this work, we show the possibility to align particles in simple microfluidic channels by exploiting viscoelastic forces in flowing suspending liquids. Experiments and simulations have been performed to investigate the effect of the channel geometry, flow rate, confinement ratio (i.e., the ratio between the particle and channel size) and fluid rheology on the particle alignment. A simple formula to design a “viscoelastic microfluidic focuser” is derived. Finally, we present experimental results on processing applications where particle alignment induced by fluid viscoelasticity is combined with magnetophoresis to deflect magnetic beads in a H-shaped channel. High-efficiency separation of magnetic and non-magnetic beads is demonstrated.