The couple, who already had a son and a daughter, were trying to sell their third child to a woman representative of an orphanage based in Udaipur, said ASP, Bhayander, Atul Kulkarni.
Police laid a trap at a restaurant in Meera-Bhayandar area and took the couple into custody along with the representative of the orphanage.
"The couple had got in touch with the woman who works for Radhika Child Care in Udaipur and wanted to sell the baby to the needy person," he said.
Mira Road Police are investigating further.
The duo have been booked under various sections of the IPC.