Massimiliano Lattore and his fellow marine Salvatore Girone shot the fishermen while serving as part of an anti-piracy mission off southern India in 2012.
The incident led to a diplomatic row between Italy and India with both marines barred from leaving India pending trial.
Lattore was finally allowed to travel back to his country last year for what Italian media reports described as a minor procedure to correct a congenital heart disease.
In April this year, he had sought and received a three-month stay from returning to India.
The Supreme Court on Monday granted him six more months in Italy for recovery while accepting his fresh application for an extension of the stay on his return order.
The other marine, Girone, is living at Italy's embassy in New Delhi.
The trial against both marines remains pending at a special court in New Delhi over confusion which agency would investigate their case. It had not opened the case when the pair was in India.
The Italian government in June announced that it had launched international arbitration proceedings in the case.
The unilateral move by the Italian government was a result of failure of direct negotiations with its Indian counterpart.
On Monday, the Italian government requested the top court in New Delhi to not hear the criminal trial of the marines as it wanted arbitration on the matter.
The Indian government told the court that it had received an arbitration notice from the Italian government and would respond to it shortly.
Ever since the incident India has insisted that the fate of the two marines must be resolved in its courts because its citizens were shot in its territorial waters.
Italy's government has argued that the shooting occurred in international waters off southern India and should be dealt under the UN Convention on the Law of the Sea (UNCLOS).