Droplet impact and spreading on solid substrates are well understood for Newtonian fluids, yet how viscoelasticity alone modifies the maximal spreading remains unclear. Here, we isolate the role of viscoelasticity by performing impact experiments with Boger fluids of comparable viscosity and surface tension but different relaxation times. For a wide range of conditions, viscoelastic droplets follow a similar behavior to Newtonian ones; however, their maximal spreading diameter is significantly reduced compared with the Newtonian behavior when the Deborah number is of order unity. This reduction is non-monotonic in the relaxation time: droplets with larger relaxation times recover Newtonian-like maximal spreading within experimental uncertainty. We rationalize these observations using an energy-balance model that includes a viscoelastic energy-storage term. The scaling argument obtained from this model explains the reported reduction in maximal spreading and identifies the range of fluid properties for which the strongest viscoelastic effects emerge.