Oestrogen receptor (ER)α immunoreactivity in three brain regions relevant to maternal behaviour (medial preoptic area, bed nucleus of the stria terminalis and medial amygdala) was measured in two species of dwarf hamster that both mate during a postpartum oestrous but differ in expression of paternal behaviour. Male and female Phodopus campbelli and Phodopus sungorus were sampled as sexually naïve adults, following mating to satiety, and as new parents. In all brain regions, females expressed higher levels of ERα than males. Species did not have an effect on ERα distribution except in the medial amygdala, where P. sungorus females had higher expression levels than all other groups. Behavioural status was not associated with altered ERα expression. These results were not expected for females and suggest that a primary activational role for oestrogen, acting through ERα in these regions, does not generalise to maternal behaviour in Phodopus. In males, these results are consistent with previous manipulations of the ERα ligand, oestrogen, and suggest that paternal behaviour in P. campbelli is likely to be regulated by developmental effects of oestrogen on the brain during early life (similar to Microtus ochrogaster), rather than through activation by oestrogen at the time of fatherhood (similar to Peromyscus californicus).