"The Mexican authorities have stated they intend to treat the arrangement as precautionary and do not intend to draw on the line," the IMF said.
It was the first line of credit approved under a new IMF program aimed at giving countries the flexibility to draw on credit at any time to prevent financial crisis.
"Today is a historic occasion. The IMF Executive Board has approved the first Flexible Credit Line (FCL) arrangement and, at the same time, the largest financial arrangement in the Fund's history," said John Lipsky, acting chairman of the IMF board.
He said the credit line was justified by Mexico's strong track record of solid growth with low inflation, steady reductions in public spending, a contained deficit, strong corporate earnings and a well capitalized banking system.
Mexico has not had to tap the IMF for credit in a decade.
"However, the current difficult global economic and financial environment poses challenges even for countries with very strong fundamentals,