Significance Recently the preoptic area (POa) has been shown to be a source of GABAergic neurons in the medial amygdala and cerebral cortex, where they are thought to play a pivotal role in emotions and intelligence, respectively. However, it is unknown how the POa-derived neurons migrate and selectively segregate into either the amygdala or cortex. By using focal in utero labeling of the POa, we show that switching on/off the transcription factor COUP-TFII (Chicken ovalbumin upstream promoter transcription factor II) and the receptor Neuropilin-2 (Nrp2) directs the POa-derived neurons toward either the amygdala or cortex. Our study revealed an essential role of COUP-TFII/Nrp2 expression dynamics in the development of the amygdala and cortex.