Local Iranian media reports that the changes were approved by the guardian council, a body tasked with ensuring that the country's judicial laws do not contravene Islamic law.
The legislation now requires only the signature of the president to be enshrined into law.
Prior to the reforms, Iran has the record for executing more juveniles than any other country in the world. A report published human rights group Human Rights Watch earlier this year stated that more than a hundred children are currently on death row. Most are not executed until they turn 18.
Stoning is usually reserved for men and women found guilty of adultery. At least 99 people have been stoned to death in Iran since 1980.
Drewery Dyke, an expert on Iran at Amnesty International, warns that due to quirks of the Iranian legal system, the reforms are not as clear cut as they appear.
"Execution is a specific legal concept in Iran. Punishment for murder in Iran under Islamic law is termed 'retribution of the soul'," Mr Dyke explains, adding that children may still be killed if charged with murder.
"Similarly with stoning, they have removed the punishment of stoning for adultery but we still don't know what manner of punishment will be proscribed in the new law. There is more to his than meets the eye – the reforms do allow for a backdoor application of stoning."
Execution sentences are routinely meted out for crimes of murder, homosexuality, adultery, drug smuggling, espionage and any perceived disruption to the economic and civil wellbeing of the country.
Amnesty International warned in December of a "killing spree of staggering proportions" being carried out in Iran, reporting that more than 600 people had been executed by the state from the beginning of 2011 until the end of November. At least three were children.
Iran 'misleading international community' with death penalty claims
Iran has been accused of misleading the international community by claiming to have abandoned the death penalty for juvenile offenders and execution by stoning for those convicted of adultery.
Local news agencies reported at the weekend that Iran's guardian council, a body of clerics and lawyers in charge of approving parliamentary activities, had approved a new amendment to the country's penal code which had been passed into law by the MPs.
The new penal code – which will come into effect after being signed by the president, Mahmoud Ahmadinejad – is believed to have been adopted in response to international criticism of Iran's violations of human rights.
But experts who have studied the new code questioned claims that the country had fully abolished the death penalty for those convicted under the age of 18 or abandoned its use of stoning. They also believe the amendments have complicated some other parts of the law, especially the punishment of homosexuality.
Sodomy for men was punishable by death for all individuals involved in consensual sexual intercourse, but under the new amendments the person who played an active role will be flogged 100 times if the sex was consensual and he was not married, but the one who played a passive role will still be put to death regardless of his marriage status.
Under the new code, the death sentence has been removed for juveniles only in crimes whose punishment can be administered at the discretion of the judge (such as drug offences). Under the same law, however, a death sentence may still be applied for a juvenile if he or she has committed crimes that are considered to be "claims of God" and therefore have mandatory sentences (such as sodomy, rape, theft, fornication, apostasy and consumption of alcohol for the third time).
Amnesty International's Iran researcher Drewery Dyke said: "Let's not be fooled by this seeming suggestion of improvements to Iran's penal code. The penal code still allows for stoning to be carried out. Child offenders are still at risk of being placed on death row, and men and women can still be convicted on grounds of consensual extramarital and same-sex relations."
