Callery pear (Pyrus calleryana) is a rapidly spreading invasive species in the central and eastern United States. This invasion is thought to comprise populations founded by hybrids between different intentionally planted P. calleryana cultivars. We investigate this scenario in an invasive population found in an urban park and natural area in Wichita, KS. Ten nuclear microsatellite loci were genotyped in invasive individuals from the park as well as planted individuals in surrounding residential neighborhoods. All invasive individuals displayed unique multilocus genotypes, none of which matched those found in planted individuals. However, in many cases potential haploid genotypes from planted individuals are hypothetical matches for one parent of invasive individuals. Taken together, these data suggest that this local invasive Callery pear population is a “hybrid swarm” resulting from gene flow among nearby, intentionally planted individuals.