Narvaez in the pink after foiling Pogacar to opening Giro stage
Narvaez stayed on Pogacar's wheel and then surged clear in a three-way sprint after an eventful 140-kilometre stage to Turin, pipping Max Schachmann and Pogacar to the line.
Ineos team-leader Geraint Thomas came in 10th, ten seconds adrift with other contenders Ben O'Connor, Damiano Caruso and Danny Martinez.
Fancied Frenchman Romain Bardet, however, dropped 57sec, which at this early stage does not yet rule him out but is far from ideal.
Narvaez was delighted with the biggest win of his career.
"You don't get many chances like that," he said of taking the pink jersey.
After denying Pogacar an eighth win in just 11 days of competitive racing this year, Narvaez said the Slovenian had made a mistake.
"He launched his sprint too early, after a hard stage like that he went from like 200m. I waited for the 100m mark," said Narvaez, who allowed Pogacar to do all the work in his bid to become the first man to win the Giro d'Italia and Tour de France double since Marco Pantani in 1998.
Pogacar was frustrated after the race.
"I had to do all the work on the hill and after that I knew Narvaez was a better sprinter. Tomorrow is better for us," he said of the mountainous run on Sunday.
UAE rider Pogacar burst from the peloton with just 3km to go but, Narvaez clung to his back wheel and only overtook 50m from the line with Pogacar crossing in third place.
This year's Giro has a punishing start with plenty of climbs over the first two stages which immediately puts the main contenders for overall victory in the mix.
There were plenty of fireworks on the opening day as big names Bardet and Ineos' Thymen Arensman were dropped off the back of the peloton on the category two Maddalena Pass climb towards the end of the race.
A six-man break built a lead of just over two minutes with 70km remaining and on the Superga climb, which was being raced on the 75th anniversary of an air disaster which killed the entire Torino football team, one of the greatest ever Italian club sides.
That gap was extended by a minute by the time Amanuel Ghebreigzabhier crossed the peak of Superga, after which Frenchman Lilian Calmejane then joined the Eritrean on the descent.
The peloton, which had been led for most of the day by Pogacar's UAE teammates, chopped that gap by half as they approached the Maddalena, a 7km climb with an average seven percent gradient.
Calmejane claimed the King of the Mountains jersey on that climb but was caught with 10km remaining.
With the peloton trailing, Pogacar made a run at the stage win but he couldn't pull completely clear, and didn't have the pace in the finale to hold off Narvaez.
Sunday's second stage is another big one for the general classification contenders as 161km of racing climaxes with a category-one climb to Santuario di Oropa.