Phytomyza rufipes Meigen (Diptera: Agromyzidae) is a leafmining pest of Brassicaceae in Europe and other regions of the world. Once reported from Oregon in the United States, this record has since been found to be a misidentification. Here we report P. rufipes for the first time from California. We compare mitochondrial cytochrome oxidase sequences of two specimens from California and one specimen from Lithuania. The two sequences from California specimens were identical and only a single nucleotide different from the Lithuanian specimen. This pattern is consistent with previous suggestions that New World populations of P. rufipes are the result of introductions. We provide information for the identification of P. rupifes using existing keys and for its discrimination from other Phytomyza in the United States.