"Starting September 1st I will run the Sciences-Po international affairs school in Paris and I will step down from my functions as an MP," he said on Italian public TV.
"I will not be stepping down from politics, but from parliament," he added.
Letta led Italy's government for ten months, but was pushed to resign in February 2014 by current Prime Minister Matteo Renzi amid political and economic crisis.
Letta was blamed for failing to carry out promised reforms in the recession-hit country and Renzi became Italy's youngest-ever premier, at 39 years old, to head a coalition government.
Sciences-Po's Paris School of International Affairs, created in 2010, "offers a cutting-edge education to tomorrow's leaders in international affairs," according to the school's website.