Five men and a juvenile had lured the 23-year-old trainee physiotherapist and her male friend on to a bus in New Delhi on December 16, 2012, before repeatedly raping the woman and beating both with a metal bar and dumping them on a road.
Mukesh, Pawan and Vinay had appealed for a review of the death sentence.
Noting that there was no evidence to show death penalty acted as a deterrent for sexual violence, the human rights body said the government must allocate adequate resources for the effective implementation of laws, improve conviction rates and ensure certainty of justice in all cases.
On September 13, a fast-track court sentenced Mukesh, Akshay, Vinay and Pawan to death.
A panel entrusted with reviewing legislation boosted the jail terms to 20 years for rape despite rejecting public appeals for the death penalty.
The court also observed that the convicts failed to point out the error in the judgement. Their sentence was upheld by the Delhi high court in 2014. That ruling came over four years after the chilling incident that took place on the night of December 16, 2012.
Jyoti Singh's parents welcomed the ruling on Monday, with her mother Asha Singh saying it was "very happy news".
The convicts now have another legal option - to file a curative petition.
The brutal crime had sparked widespread protests and drew worldwide attention over violence against women in India. At the time, due to Indian laws that prohibit the naming of rape victims, sections of the media referred to Singh as "Nirbhaya", which means fearless, a nod to her determination to survive in the days after the incident.
One of the accused in the case, Ram Singh, had allegedly committed suicide in the Tihar Jail here.
Over the next few days, his brother Mukesh Singh, gym instructor Vinay Sharma, fruit seller Pawan Gupta, a helper on the bus Akshay Thakur, and the 17-year-old juvenile, who can not be named, are arrested. She died two weeks later of injuries in a hospital in Singapore, where she had been taken for treatment.
According to National Crime Records Bureau data for 2016, incidents of rape of children in India increased by over 82 percent compared with 2015, when almost 35,000 rape cases were reported to the police.
The case led to the introduction of the death sentence for raping girls under 12. "What has happened between the confirmation of death sentence and now - there is no diminution of sexual violence against women", Grower said.