Speaking at a clinic Sunday in Senegal, Harper said the federal government's contribution to the Micronutrient Initiative will help deliver an estimated 400 million vitamin A and zinc supplements per year to kids under the age of five.
He said helping improve the health of mothers, newborns and children is the "top international-development priority" for his government.
"We're acutely aware of how much work remains to be done to improve maternal and child health, and we will keep raising this issue at every opportunity in Canada and on the world stage," said Harper, who was in the west African country to attend the summit of la Francophonie, a network of 57 French-speaking countries and jurisdictions.
"There is simply too much at stake to remain silent. We know how many lives can be saved, we know how to do it, and so friends we must get it done."
He said the Canadian-based Micronutrient Initiative, an international non-profit organization, has helped save four million lives in its battle against vitamin and mineral deficiencies.
The government said the investment announced Sunday will increase the production of iodized salt to reach an estimated 120 million people each year.
It will also allow the organization to administer iron and folic acid supplements to approximately 80 per cent of pregnant women in communities targeted by the program, primarily sub-Saharan Africa and South Asia.
Eighty per cent of the $150 million is part of a $3.5-billion fund the Conservatives announced last May at a summit in Toronto aimed at financing Canada's maternal, newborn and child health strategy from 2016-2020.
The contribution followed Harper's announcement Friday during the summit that Ottawa had earmarked $500 million for a program aimed at providing vaccines for impoverished children around the world. That money will also come from the $3.5-billion fund.
On Sunday, Harper said he provided the program's eight-billionth vitamin A capsule to a child at the clinic.
"This situation is particularly crucial in these countries of la Francophonie that are afflicted by the highest rates of malnutrition and infant mortality in the world," he said.
Following Sunday's announcement, Harper was asked at a news conference whether he thought some member countries of la Francophonie should be expelled because they had been accused of violating human rights.
In his reply, he drew a comparison between la Francophonie and the Commonwealth.
"The Francophonie in recent years has in fact, as you know, been suspending countries that have failed to live up to basic democratic norms. This is a big advance," Harper told reporters.
"I would point out, much to our disappointment, the Commonwealth has been moving in the opposite direction, while the Francophonie has been moving in this direction."
Harper boycotted the most recent Commonwealth leaders' summit in Sri Lanka because the country's government wouldn't agree to an independent international investigation into allegations of war crimes committed by its military against Tamil rebels at the end of its civil war.
On Sunday, he credited la Francophonie for having an "increased focus on human rights and democratic norms" in recent years and for adding three observer countries with strong democratic records over the last generation: Costa Rica, Mexico and Kosovo.