Marcelo called Fluminense's success in the Copa Libertadores final on Saturday the biggest title of his career, ahead of Real Madrid's Champions League wins.
Rio de Janeiro-based Fluminense, Marcelo's boyhood team, claimed its first title in the CONMEBOL South American club competition after a feisty 2-1 win over Argentina's Boca Juniors after extra time.
The Brazilian left-back, 35, won five Champions League titles with Real Madrid during a distinguished 15-year career with the Spanish giants, but revealed that this one meant more because of his boyhood attachment to Fluminense.
Marcelo told ESPN: 'Real Madrid will understand. It's my most important title, at club level, because it's the club that raised me.
'I'm winning a very important title with my favourite club, the club that gave me all the tools to have my career, with the employees who saw me grow up. There's nothing more rewarding than that. It's priceless.
'I owed a debt to Fluminense. It was written [that we would win the trophy]. There's nothing else to say.
'Many people criticised us, but today Fluminense is the Copa Libertadores champion. ... Earlier I was crying, I was nervous, but now it is all about happiness.'
Marcelo started as a youth player at Fluminense in 2002 before breaking into the first team.
In 2007, he moved to Real Madrid, where across a decade and a half, he won five Champions League trophies, six LaLiga titles, five Spanish Super Cups, four Club World Cups, three European Super Cups and two Copa del Rey trophies.
After leaving Spain last year, he had a spell with Greek side Olympiacos, before returning to his boyhood club in Rio in February.
Marcelo started Saturday's final, and was substituted at half-time when Fluminense were 1-0 up courtesy of German Cano's 36th minute goal.
Boca Juniors' Luis Advincula equalised 18 minutes from time to send the game to extra time.
Substitute John Kennedy hit a superb volleyed strike to put the Brazilian side ahead - only to receive a second booking for celebrating with the crowd, reducing Fluminense to ten men.
As Boca Juniors looked to get back level with a man advantage, Frank Fabra was also shown a red card after a VAR review confirmed he slapped a player.
Fluminense held on, which means Marcelo has joined a group of just 15 players to conquer both intercontinental club tournaments, alongside Ronaldinho, Neymar and Julian Alvarez.
Brazilian clubs have now won the last five editions of the Copa Libertadores, with Flamengo prevailing in 2019 and 2022, and Palmeiras earning back-to-back titles in 2020 and 2021.