Mothers experience dramatic physiological changes during pregnancy and lactation, and some of these modulations persist for a very long time. Here we showed that female mice prefer a cooler environment starting from late pregnancy and persisting long term postpartum. Female mice with reproductive experience (RE, > 4 weeks post-weaning) displayed lower body temperature and a lower thermal preferred temperature, and lost preference for warm environments (30 °C) but preserved avoidance of cold environments (15 °C). This was associated with a significant decrease in estrogen receptor alpha (ERα)-expressing neurons in the preoptic area (POA), a brain region important for thermosensing and thermoregulation. Importantly, the deletion of ERα from the POA in virgin female mice reduced thermal preferred temperature and warm preference, mimicking RE mice. We further found that distinct ERα^POA subpopulations can be regulated by temperature changes with or without presynaptic blockers, and by ERα agonist. More importantly, RE decreased the number of warm-activated ERα^POA neurons and reduced the excitatory effects of warmth and estrogen-ERα signaling, while cold-activated ERα^POA neurons were slightly enhanced in female mice with RE. Together, our results support that the thermosensing ability and estrogenic effects in ERα^POA neurons are regulated by reproductive experience, altering thermal preference.