Christine Lagarde said stimulus policies were still needed in some regions, especially Europe and Japan.
With signs that the global economy is improving, there has been much debate about when supportive policies should be wound down.
But, in a speech in the US, Ms Lagarde said she did not suggest a "rush to the exit" as some economies remain fragile.
The US Federal Reserve has signalled it may slow down its
huge monthly bond buying programme, a suggestion that has hit stock
markets and currencies around the world.
But Ms Lagarde said stimulative measures had been successful and were still necessary in key economies.
Any withdrawal should be determined by the strength of individual economies, she said. Read more...
