The team said he died Tuesday night at a Los Angeles hospital, but did not provide the cause or other details.
Dodger Stadium was lit up in blue in honor of the left-hander who had his No. 34 retired by the team in 2023.
Fans stopped outside the ballpark to share memories and drop off flowers for the beloved Dodgers icon.
"Fernando Valenzula is from Sonora where my family is from. My mother was so proud and happy. She came to all the games, and she brought us along," Marcia Cagigas told Eyewitness News outside of Dodger Stadium.
Valenzuela's rise from humble beginnings as the youngest of 12 children in Mexico and his feats on the mound made him hugely popular and influential in Los Angeles' Latino community while helping attract new fans to Major League Baseball. Their fondness for him continued for years after his retirement.
"He was a gentleman all the way around. He was just so humble," actor and Los Angeles native Danny Trejo said. "I think he refused to think of himself as great, but he was. The humility came when you gave him a compliment and his face would almost get red."
Danny Trejo reflects on legacy of Dodgers icon Fernando Valenzuela
"63 is way too young.... A piece of my childhood is gone," actor Mario Lopez posted on X. "Growing up as a Mexican kid one of the main reasons I'm a Dodgers fan is because of Fernando. ... Not only a great player, but a great man to the community. What a legend."
L.A. Mayor Karen Bass called Valenzuela a legend and "a world champion - through and through."
"To millions, Fernando Valenzuela was more than a baseball player," Bass posted on X. "He was an icon that transcended the limits of hope and dreams. He was the voice of a game that we hold close in our hearts. His charisma was palpable, and his excellence was undeniable."
California Sen. Alex Padilla posted on X: "You can't tell the story of Dodgers baseball without Fernandomania. El Toro was a hero to our community on & off the mound, & he leaves behind an indelible legacy. My thoughts are with his family during this time."
The baseball summer league as well other sports entities in Mexico, including the Mexican Soccer Federation and the National Sports Commission, also mourned his death.
"I think we, all Mexicans, are sad for the Valenzuela loss, and we express our solidarity with his family," new Mexican President Claudia Sheinbaum said at her daily news conference.
Valenzuela is not only considered Mexico's greatest baseball player, but he also is widely considered one of its top three athletes of all time, along with soccer player Hugo Sánchez and boxer Julio César Chávez.
"It's a sad night. The news has shocked me, my soul and my spirit, it's a tremendous loss," said Sánchez, now a sports analyst for ESPN. "He was a symbol for Mexican sports during a historic moment."
His performances created the delirium known as "Fernandomania" among Dodgers fans. The ABBA hit "Fernando" would play as he warmed up on the mound.
"Fernando Valenzuela was a true icon of the Dodgers and the game," Rep. Jimmy Gomez posted on X. "His legacy and connection with the Latino community in LA is one of the reasons I fell in love with the Dodgers."
Commissioner Rob Manfred said Valenzuela would be honored during the World Series at Dodger Stadium.
The Dodgers named Valenzuela as part of the "Legends of Dodger Baseball" in 2019 and inducted him into the team's Ring of Honor in 2023.
The Associated Press contributed to this report.