Sergio Coronado left Chile with his family after the coup d’état of General Pinochet in 1973. He grew up in Argentina, and arrived in France in 1982. At the end of 2008, he won a scholarship in political science, and moved to Bogotá, Colombia. He attends the Universidad Externado de Colombia, and joins the ADFE-Français du Monde association.
In June 2012, on the occasion of the Pride parade, he came out as gay on Twitter. This is the 2nd MP to do it publicly.
He joined the Greens in 1998, and joined the Executive College. He was re-elected for three successive terms in 2000, 2002 and 2004 in various capacities. He was notably co-spokesman of the party with Cécile Duflot from January 2005 to January 2008, after almost becoming national secretary at the Reims Federal Assembly in 2004. In 2002, Noël Mamère chose him as director of communication and deputy campaign manager for his presidential campaign.
From March 2001 to March 2008, he was the elected municipal of the 14th arrondissement of Paris on a list of rally of the left and ecologists. As deputy mayor, he was in charge of local democracy, associative life and neighborhood councils.
At the 2011 Europe Ecology – The Greens primary, he was Eva Joly‘s campaign director. Once invested by the ecologists, she makes it one of its four spokespersons, alongside José Bové, Dominique Voynet and Michèle Rivasi, and its director of communication.