The effect of stretch in polydisperse spray flames is investigated for the first time, in the context of a spherically symmetric laminar flame propagating into a mixture of fuel vapor, droplets, and air. The study reveals that, in addition to the well-known (gas) Lewis number effect, there is a pronounced effect resulting from the presence of the spray, which causes acceleration of the flame due to droplet evaporation. For mixture Lewis numbers equal to or greater than unity, the two effects combine to bring about flame acceleration. However, in mixtures having Lewis numbers less than 1, the two effects become competitive-the Lewis number effect tending to decelerate the flame, while the spray effect accelerates it. For highly volatile sprays the Lewis number effect is dominant, but for less volatile sprays the behavior is different. The relative importance of the two effects changes dynamically in time, and, beyond some instant after ignition, the spray evaporation effect is completely dominant, causing flame acceleration for any Lewis number, in sharp contrast to the behavior of an equivalent gaseous fame.