The formation of attachments between mated pairs is a defining feature of monogamous mating systems. Decades of research using microtine voles (genus Microtus) have uncovered many of the brain regions and pathways critical for the formation and maintenance of these bonds in monogamous mammals. Several studies have also explored the function of specific candidate genes in bonding, particularly the nonapeptides and their receptors, as well as dopamine and opioid receptors. However, so far, the greater gene expression changes that occur in response to and support of pair bond formation have not been more thoroughly explored. We used RNA-sequencing to observe changes in gene expression in response to mating in three brain regions critical for pair bond formation in two related species: the pairbonding prairie vole (M. ochrogaster), and the promiscuous meadow vole (M. pennsylvanicus). We sequenced transcripts from the amygdala, hypothalamus, and a region inclusive of the ventral pallidum and nucleus accumbens in virgins and at three time points after the onset of mating in both species. Differences in gene expression patterns were most strongly associated with species and brain region. We identified differential expression of gene categories across species and brain region and found specific genes that differ in expression in response to mating across species. In addition, we identified gene modules strongly associated with brain regions, as well as modules that correlated significantly with mating status in prairie voles, but not meadow voles. These results emphasize the importance of pre-mating differences in gene expression that confer the capacity to bond in prairie voles and identify new candidate genes which may play an important role in bond formation.