The 49-year-old won the party's primary with 54 percent of the vote, defeating fellow MEP Michèle Rivasi who took 40.75 percent.
An environmentalist and humanitarian who coordinated Greenpeace campaigns in France between 2002 and 2008, Jadot was elected to the European Parliament in 2009.
Cécile Duflot, a former ecology minister in President Francois Hollande's Socialist government, had been considered the frontrunner but was knocked out in the first round of the EELV primary on 19 October.
The Greens have suffered a number of defections of MPs who were keen to keep collaborating with the Socialists after Duflot quit the government.
The presidential vote is set for 23 April and 7 May.