The papaya mealybug, Paracoccus marginatus Williams & Granara de Willink (Hemiptera: Pseudococcidae), highly polyphagous and now widespread, was discovered in Mengla County, Yunnan Province, China. The present study is aimed at confirming the identity of P. marginatus in mainland China based on its morphology and using molecular methods. Mitochondrial genes for cytochrome oxidase I (CO-I) were sequenced from 2 samples of P. marginatus. Homologous DNA sequences of P. marginatus, Phenacoccus solenopsis Tinsley and Coccus viridis (Green) (Hemiptera: Coccidae) - as an outgroup -were downloaded from Gen Bank. The morphology of putative P. marginatus specimens was examined using the same specimens as were subsequently used for the molecular study. Key morphological traits are described and illustrated. A 746 bp fragment of the CO-I was analyzed for the identification of P. marginatus. A phylogenetic tree was generated with the DNA sequences of all the mealybug species used in this study. The tree included 2 distinct clades: one consisting of the samples of P. marginatus and the other consisting of P. solenopsis. The phylogenetic tree and the sequences indicated that P. marginatus collected on papaya had 99% similarity with the other 3 accessions found through the BLAST search. Identification information may help strengthen quarantine programs to protect agroforestry production and maintain the ecological balance in China.