Mukesh Sakat (20), the main accused, knew the boy's parents, and hatched the plan to kidnap because he wanted money to gain entry into Bollywood, police said.
The kidnappers, however, panicked and abandoned the boy a few hours after taking him away.
Sakat, Mukesh Rajput (19) and Bhavesh Bhoir (19) were nabbed on the intervening night of August 24 and 25, said additional Superintendent of Police Dr Raj Tilak Roshan today. Two other accomplices of Sakat were absconding.
The boy was abducted from near his house in Nalasopara in the district on the afternoon of August 24. Kidnappers called the parents and demanded Rs 6 lakh in ransom, to be handed over at Churchgate in Mumbai.
Police found him and reunited him with his parents. Subsequently Sakat, Rajput and Bhoir were nabbed, while a hunt is on for two others involved in the crime.