The 65-year-old Italian, who left Real Madrid at the end of the European season, has been charged with taking Brazil through the latter stages of qualifying for the 2026 World Cup.
The former AC Milan and Chelsea manager replaced Dorival Junior, who was sacked at the end of March after the 4-1 thrashing at the hands of reigning champions and bitter rivals Argentina.
Thursday’s result leaves the Selecao in fourth place in the qualifying table on 22 points while Ecuador, the surprise package in the campaign, remain in second place on 24 points.
Argentina, who face Chile later on Thursday, lead the standings on 32 points and are the only team to have officially secured their place in the tournament which will be held in the USA, Canada and Mexico.
Paraguay, who enjoyed a 2-0 win over Marcelo Bielsa’s Uruguay, sit in third place, level on points with Ecuador.
Ecuador knew a win would put them on the brink of qualification and there was a packed crowd at the Estadio Monumental in Guayaquil.
But the home side were dealt a blow just before kick-off when goalkeeper Hernan Galindez suffered a muscle strain in the warm-up and replacement Gonzalo Valle was hurriedly sent out to make his debut.
If Valle had any nerves they eased when he did well to parry a shot from inside the box from Vinicius Jr. who had been set up by Gerson following a turnover.
Chances were limited in a contest where neither side was able to get control of midfield.
The pattern continued after the break with Ecuador, missing their injured striker and talisman Enner Valencia, struggling to pose a threat.
Real Madrid star Vinicius was quiet for much of the game and with Rodrygo absent, Brazil also lacked potency in attack.
The best opening came in the 75th minute when Vinicius broke down the left and cut back to Casemiro, but the Manchester United midfielder, recalled to the national side by Ancelotti, saw a tame side-footed effort easily dealt with by Valle.
While there was no instant impact from Ancelotti, Vinicius, who played under the coach in Madrid, said he needed time to make his impact felt.
“I’m very happy to have Ancelotti here with us, because I’ve always said he’s the best coach I’ve ever worked with. Having the opportunity to work with him in the Brazilian national team is the best,” the winger said.
“He hasn’t had time to show his work, his game plan, because he’s only had two or three days of training,” he added.
A header from midfielder Matías Galarza just 13 minutes into the game and a late penalty from Julio Enciso earned Paraguay a crucial victory over a depleted Uruguay.
The victory left Paraguay on the verge of securing their return to the World Cup for the first time since qualifying for the 2010 finals in South Africa.
Victory in Sao Paulo on Tuesday against Brazil would secure their place in the tournament.
The top six teams in the 10-team qualifying group head directly into the World Cup draw, while the seventh placed team must enter the inter-confederation playoffs. (AFP)