The cellular diversity of neurons located in the marginal zone (MZ) of the cortex has a crucial role in cortical development. However, little is known about the molecular mechanisms involved in how these different neuronal cell types are specified. Here, we show that in the MZ, the nuclear receptor COUP-TFI is localized in calbindin-positive cells and not in reelin-positive cells. High expression of COUP-TFI has been detected in preplate (PP) and subplate (SP) cells, suggesting that this nuclear receptor is down-regulated during preplate differentiation towards the Cajal-Retzius (CR) cell lineage. By maintaining high ectopic expression of COUP-TFI in preplate cells, we show that COUP-TFI represses the CR cell markers reelin and calretinin, and with lower efficiency the transcription factor Tbr1. Furthermore, general differentiation is not affected, strongly suggesting that COUP-TFI represses differentiation of CR cells.