Quintana, who turned 36 in February, is an icon in Colombia as much for his easygoing manner as for winning the Giro d'Italia in 2014 and the Vuelta a España in 2016.
He came second in the Tour de France behind Chris Froome in 2013 and 2015, and third in 2016.
"This is my last season as a professional cyclist, and every race will be a last dance," said the Colombian.
Speaking ahead of next week's Tour of Catalonia, the Movistar rider said his one-year extension with the Spanish team would be his last year.
He raced 20 Grand Tours but was generally in the shadow of the cycling superpower Team Sky.