In biological invasions, multiple paternity can preserve genetic diversity over time and space and contribute to invasion success. Therefore, knowledge on the mating system of invasive species is essential to develop adequate management practices to mitigate their impact on ecosystems. The spotted lanternfly, Lycorma delicatula (White, 1845), is an invasive pest that has colonized more than 10 eastern US states in less than 10 yr. Multiple paternity may contribute to its success, but little is known about spotted lanternfly's mating system. We explored the mating system using mated females and female–egg mass pairs sampled in the field. First, we assessed the existence of multiple mating by counting the number of spermatophores in the genital tract of all females. Second, we searched for genetic evidence for multiple paternity within egg masses by genotyping the female–egg mass pairs at 7 microsatellite loci. Third, we assessed whether multiple mating was correlated with female traits and distance from the introduction site. One to 3 spermatophores per female were found during dissections, confirming the existence of polyandrous female spotted lanternfly. We found genetic evidence for a minimum of 2 fathers in 4 egg masses associated with polyandrous females, validating multiple paternity in spotted lanternfly. Multiple paternity was associated with egg mass size, and multiple paternity was highest in populations closest to the original introduction site and decreased toward the invasion front. Multiple paternity may contribute to the invasion success of spotted lanternfly, and control efforts should consider the mating system and the implications of its spatial patterns.