The five-time European champions have fallen short in the continent's premier club competition in recent seasons, including extraordinary losses to Liverpool and Roma in the knockout rounds over the last two seasons.
The Catalan club have remained a dominant force in Spain, having won the league in four of the last five seasons, but the club have only reached the final of Europe's premier club competition once in the last seven years, having reached the showpiece three times in the seven years prior.
Ancelotti, whose side face Barca in a friendly in Florida on Wednesday, feels Ernesto Valverde's men should be contenders once more this season after seeing the likes of Antoine Griezmann and Frenkie de Jong arrive to bolster a squad that still includes Lionel Messi.
"I believe that Barcelona is always a candidate to win the Champions League," he told a news conference.
"It has a player like [Lionel] Messi and many others, so I think they always compete to win the maximum and the maximum is the Champions League.
"I think that with the signings they have done, this year will be very competitive."
Napoli are also looking to move forward after finishing second in Serie A and getting knocked out in the Champions League group stage.
And while the manager believes Serie A is on the rise, he conceded that the Premier League and La Liga, which produced eight of the last 10 Champions League winners, remain the world's best domestic competitions.
"At the moment, Italian football is a little below La Liga and the Premier League, but something is moving," he said.
"Last year Cristiano [Ronaldo] arrived [at Juventus], which is very important for our league. I think in the future Italian football is going to reach the level.
"The stadiums are being renovated and I think that little by little Italy will be better."
Napoli open their Serie A season on August 24 against Fiorentina as they look to put an end to Juve's dominance of the league where they have claimed the title in each of the last eight seasons.