Many are on the brink of starvation amid the strict regime and the worst drought in 30 years.
World Vision New Zealand national director Grant Bayldon said Afghanistan was now likely the world's worst humanitarian crisis.
"[Years of drought] mean crops have failed and then with the Ukraine crisis going on, it's meaning that the price of grain and getting it into Afghanistan has skyrocketed. People have less money and food is more expensive," he said.
The average household income was just $1 per day.
More than 800 Afghan parents, caregivers, and children were surveyed for the report across four provinces - with over half the children classed as acutely malnourished.
"What it means is children don't have enough nutrition to be able to be healthy, to be able to grow, to be able to sustain themselves. Many of those families will be approaching starvation or acute hunger," Bayldon explained.
Some parents faced the horrendous decision of marrying off their children to survive.
"If they can marry a child to a family that can afford to feed that child, then it's one less mouth to feed. Also, in some circumstances, there's some kind of dowry or payment that comes with the marriage for the child which can help parents to feed their remaining children."
The average age for a child to have an arranged marriage was 12 or 13 but it did happen to younger children too, he said.
"Child marriage is something that we see spike when families are under extreme stress."
And 75 percent of boys and 50 percent of girls have also stopped going to school, instead working to help support their families.
The report also found social stigma prevented people from publicly admitting their hunger.
Bayldon said more funding was desperately needed to provide aid to suffering families.
"While governments and decision-makers around the world have prioritised other emergencies, the children of Afghanistan have been largely forgotten. We are calling on the international community to take the necessary action to support Afghanistan's people so that they can recover and rebuild from this devastating humanitarian crisis."
Further funding was critical to allow life-saving food, water and health services to continue, he said.