"The debate on the debt cancellation was never opened. I do not think it is necessary to open it if things go well," Lagarde told the Swiss Le Temps newspaper.
Lagarde reaffirmed her commitment to taking measures in respect of debt relief for Athens.
"There are talks about extending maturities, reducing rates for a certain period. We are not talking about debt cancellation," she said.
The IMF is one of Greece's main international lenders, alongside the European Central Bank and Eurozone states. Athens is struggling to restructure its multibillion debt.
Shortly after that, Lagarde welcomed the decision to provide Greece with a new financial aid package, and insisted that additional relief was necessary to ensure the country's medium and long-term debt sustainability.
Lagarde did not specify whether the IMF would be engaged in Greece's freshly agreed bailout deal.