Other countries that reported progress in tackling child deaths include Liberia and Rwanda, the charity said.
Child mortality rates in Niger fell by almost two thirds because of government policies to curb hunger and poor healthcare, it added.
Niger was hit by a severe drought in 2005, causing widespread hunger.
It led to aid agencies launching an international campaign to feed hundreds of thousands of people.
However, Niger has managed to reduce the deaths of children under the age of five from 326 in 1,000 in 1990 to 114 in 1,000 in 2012, Save the Children says.
At the other end of the spectrum lie Haiti, Papua New Guinea and Equatorial Guinea with slow and unequal reductions in under-five mortality rates”
“Despite having scarce resources and recurring droughts, Niger has cut the number of under-fives dying unnecessarily by nearly two-thirds since 1990 and is on track to achieve the UN’s global goal on child mortality,” it added in a statement.
The charity’s West Africa director, Ms Natasha Quist, told the BBC’s Focus on Africa radio programme that Niger’s government was fulfilling its promise to give free healthcare to pregnant women.
“They’ve declared it and they’re doing it,” she said.
Many women in remote parts of Niger now had access to clinics, Ms Quist said.
The government has also implemented effective farming policies, in a radical change from the situation in 2005 when there was “no food, no grain”, she said.
Other African countries that have significantly reduced child mortality include Madagascar, Egypt and Tanzania.
Outside Africa, progress has been reported in China, India and Indonesia, Save the Children says.
“At the other end of the spectrum lie Haiti, Papua New Guinea and Equatorial Guinea, with slow and unequal reductions in under-five mortality rates and low levels of investment in health and nutrition.”
Credit: BBC & Africareview.com