TOM22 is a core component of the mitochondrial protein import complex, spanning the outer mitochondrial membrane. As a tail-anchored protein, TOM22 is inserted into mitochondria post-translationally. The sequence of TOM22, however, allows it to be inserted into the endoplasmic reticulum, if the C-terminus is masked by another sequence or if there is a mutation in the transmembrane domain. Here we report that C- and N- terminal fluorescent protein fusions of TOM22 preferentially localize to the endoplasmic reticulum in mammalian cells. Our finding has relevance for cell biological studies that use TOM22 as a mitochondrial marker, and for attempts to understand the mechanism of TOM22 mitochondrial insertion.