Needle nematode populations ofLongidorus orientalisassociated with date palm,Phoenix dactylifera, and detected during nematode surveys conducted in Arizona, California and Florida, USA, were characterised morphologically and molecularly. The nematode species most likely arrived in California a century ago with propagative date palms from the Middle East and eventually spread to Florida on ornamental date palms that were shipped from Arizona and California. This is the first validated continental record of this needle nematode species in the USA and the Americas. The USA populations ofL. orientaliscontained a small number of males that were not reported in the original description and are herein described.Longidorus orientaliswas able to survive for at least 4 years at very low numbers in the warm and humid environment of Florida on date palms imported from California and Arizona. Association ofL. orientaliswithL. africanuswas observed in all of the surveyed sites, indicating that date palm is a host of both nematodes. Phylogenetic relationships ofL. orientaliswith closely relatedLongidorusspecies, in addition to relationships between populations ofL. orientalisfrom the USA, Greece, Iran and Spain, were inferred from the analyses of D2-D3 of 28S rRNA, ITS1 rRNA and partialcoxIgene sequences. The PCR-D2-D3 expansion segments of 28S rDNA-RFLP diagnostic profile is provided.Longidorus orientalispopulations display a high level of intraspecific variation (up to 15.5%) incoxImtDNA sequences. Analysis of phylogenetic relationships of nematode populations revealed incongruence of the ITS1 rRNA andcoxImtDNA gene trees, which might be the result of selective introgression of mtDNA through gene flow between previously isolated populations introduced simultaneously into new geographical regions.