The contest, set for April 13, will be a repeat of the October 2023 snap election that earned Noboa a 16-month presidency.
Noboa and González are now vying for a full four-year term, promising voters to reduce the widespread criminal activity that upended their lives four years ago.
Figures released by Ecuador's National Electoral Council showed that with 80 per cent of ballots tallied, Noboa received more than 3.71 million votes, or 44.43 per cent, while González earned over 3.69 million votes, or 44.17 per cent.
The 14 other candidates in the race were far behind them.
The 37-year-old heir to a business fortune, Noboa has said his deployment of the military on the streets and in prisons, among other measures, reduced violent deaths by 15 per cent, damped prison violence and aided the capture of major gang leaders.
But leftist Gonzalez, 47, and Noboa's other 14 first round rivals called for more efforts to fight the drug trade-related crime that has rocked Ecuador in recent years.
Gonzalez, a protege of former President Rafael Correa, has said she would tackle crime with major military and police operations, pursue corrupt judges and prosecutors, and roll out a social spending plan in the most violent areas.
"This triumph is for you because Daniel Noboa represents fear and we represent hope, change, the hope of transforming the country," Gonzalez told supporters in Quito.
"We are nearly in a technical tie, with a trend, which is the most important, where we will keep growing in votes and Daniel Noboa will keep falling in votes."
For days, Correa and Gonzalez have been decrying what they called plans to commit election fraud, with Gonzalez singling out Atamaint, saying she had allowed Noboa to ignore campaigning rules.
Noboa did not speak to awaiting supporters in Quito.
He has been embroiled in a long-running spat with his vice president, most recently over whether and how he could take campaign leave.
This week, the constitutional court held invalid two decrees that Noboa used to take campaign leave in the first round, a ruling likely to complicate his ability to name an interim vice president so he can campaign ahead of the run-off.
Noboa unveiled several 11th-hour policies seemingly designed to attract voters, from help for migrants returning from the United States to tariffs on Mexican imports and a trade deal with Canada.
with AP
