Some pilot projects of polymer injection in oil fiel ds have shown an increase in oil recovery, although the mechanisms that govern the flow dynamics are still not well understood. Recent experimental investigations have shown that the viscoelastic properties of polymer solutions may change the pore-scale flow behavior and reduce the residual oil saturation. To understand these phenomena in porous media, it is important to understand viscoelastic flow behavior through the pores-throats. This work presents experimental study of the flow of a high molecular viscoelastic PEO solution (0.1 wt percent Polyethylene Oxide) flowing through a constricted capillary, used as model for a pore-throat geometry of a porous media. Pressure drop measurements are performed and velocity fields are obtained using the micro-particle image velocimetry (Micro-PIV) technique. Experiments with a viscous solution of glycerin (45 wt percent glycerin in water), of similar shear viscosity to the PEO solution were also performed in order to isolate the elastic effects of the PEO solution. The flow of the PEO solution exhibited an extra pressure drop (nonlinear behavior) above a critical flow condition beyond which the elastic forces become relevant. For the entire flow rate range explored, the velocity field of the glycerin solution showed a Newtonian flow regime, while the PEO solution shows instability in the flow above a critical Weissenberg number, coinciding with the onset of the extra pressure drop. This instability in the flow is associated with the high extensional viscosity near the constriction at high enough extension rates. The results show the changes in the flow pattern of the PEO polymer solution due to the presence of the elastic effects of polymer, and provide important information on how viscoelastic polymer solutions behave in a porous media and can impact their use in Enhanced Oil Recovery operations.