The US, which is second only to Mexico in the UN children's agency report, is nonetheless one of few countries to see a recent decline in child poverty.
In total, Unicef says up to 50 million children are living in poverty in rich nations and the figure is rising.
Children in Nordic countries are best off, due to higher social spending.
Unicef looked at 24 of the 30 states in the Organisation for Economic Cooperation and Development (OECD) - a Paris-based group of the world's wealthiest nations.
The figures refer to relative poverty defined as households with income per head below 50% of the national average.
Its Child Poverty in Rich Countries report found that the number of children living in poverty had risen in 17 of those countries over the past decade.
Mexico comes bottom of the table with a figure of 28%.
"No matter which of the commonly used poverty measures is applied, the situation of children is seen to have deteriorated over the last decade," the report says.
Rest of the story
That has to be a joke, in these statistics the US and Mexico (the two with the most child poverty) have problem with it.
US has a GDP per capita close to US$37,800, meaning that a child with an income of less than 50% of the average is living with less than US$18,900 I don't know about the cost of living there but it doesn't seem THAT low.
Mexico has a GDP per capita of about US$9,000, but this number is an EXTREMELY bad average, sure if you sum each incomes and divide you'll get this, but Mexico being a country with more billionaries than France and with people as poor as those in Africa, the number is, to say the less, unreal. USD9,000 a year is the income for middle low class, USD4,500 is high-low but not poverty. And yet they claim that one out of 3 kids is poor here, I'd venture to say that one in five.
And I wonder how El Salvador and Guatemala ranked there