Their support to the planned $400 billion fund-raising exercise "clearly demonstrates these countries' enduring commitment to multilateralism," Lagarde said in a statement.
"Ensuring that the Fund has sufficient resources to tackle crises and to promote global economic stability is in the interests of all our members," she said.
In a Frankfurt Allgemeine Zeitung interview published earlier Tuesday, Lagarde revealed that the International Monetary Fund is seeking some $400 billion for expanding its crisis intervention "firepower".
That was sharply lower than the original target of $500 billion. Last week Lagarde said the Fund was lowering its target, citing a slight easing of tensions in the global and eurozone financial system.
In the newest pledges, Denmark was promising about $7 billion, Norway $9.3 billion, and Sweden, $10 billion.
Their contributions follow a $60 billion commitment from Japan and $200 billion from the euro area.
The IMF is hoping to firm up commitments, especially from the big emerging economies like China, Russia, Brazil and India, at the Fund's Spring meetings held at the end of this week in Washington.
But the Fund's largest shareholder, the United States, is not expected to contribute.