The country's Senate passed the measure in December, and it now goes to King Philippe to be signed into law, CNN reported.
The report said the measure has wide support, but it has evoked strong opposition from critics.
Belgium legalized euthanasia in 2002, but only for those who are in "constant and unbearable physical or mental suffering that cannot be alleviated."
The new measure extends that right to those under 18 under strict conditions, CNN said. A minor must be able to understand what euthanasia means, and consent must come from parents or guardians.
Linda van Roy said she wished euthanasia had been an option for her 10-month-old daughter, who died under heavy sedation and in pain at 10 months old from Krabbe disease. Her daughter, Ella-Louise, would not have qualified for euthanasia under the conditions set by the measure, but van Roy said she still supports the legislation.
"We want for those [older] children to be able to talk about euthanasia and to ask those questions and if they really want to say, 'Stop. This is it. I don't want it any more,' that they can have a choice," she said.
Palliative care nurse Sonja Develter said she worries children can't understand the consequences of euthanasia and fears they would make the decision based on what they think their families want to hear.