The 10 a.m. Mass was open to the public on a first-come basis due to limited capacity inside the church on West Temple Street.
Valenzuela, the 1981 NL Rookie of the Year and Cy Young Award winner, died at age 63 on Oct. 22, one day shy of the 43rd anniversary of his 147-pitch complete game that led the Dodgers over the Yankees in World Series Game 3.
Valenzuela was on the minds of the Dodgers and Yankees during Game 1 of this year's World Series.
An informal memorial at a sign welcoming fans to Dodger Stadium that popped up soon after the pitcher's death on Oct. 22 was still going strong three days later. Large blue-and-white floral arrangements, including "34" representing his jersey number, were propped on the corner near the entrance to the stadium.
A video highlighting Valenzuela's career opened the pregame ceremonies. A mariachi group from his native state of Sonora in Mexico played as photos from his career flashed on the videoboards. The mix of guitars, trumpets and violins grew from somber to upbeat.
Ballpark flags were lowered to half-staff. During a moment of silence, fans chanted "Fernando!" in Valenzuela's honor before the first pitch. Some wore sombreros.
Dodgers icon Fernando Valenzuela remembered by fans on his birthday
Orel Hershiser and Steve Yeager, former teammates of Valenzuela, didn't throw the ceremonial first pitch. Instead, Hershiser placed the ball on the back of the mound, where No. 34 was etched.
Valenzuela's wife, Linda, and their four children joined manager Dave Roberts as the Dodgers lined up along third base before the national anthem performed by Brad Paisley.
Fans crowded around a large white wallboard to write messages in remembrance.
The Dodgers wore a No. 34 patch on their uniform sleeves during the World Series and will continue to do so through the 2025 season.
"If there's two people that probably impacted this organization most, I think you would say Jackie Robinson and Fernando Valenzuela," Roberts said. "No disrespect to anyone else, but if you're talking about currently the fan base, there's a lot of people that are here and support the Dodgers south of the border because of Fernando."
Roberts was just 9 years old when Valenzuela and his unique eyes-to-the-sky delivery led to "Fernandomania." In 1981, the Mexican-born left-hander won the National League Cy Young Award and Rookie of the Year, still the only player to do so.
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He had worked on the team's Spanish-language broadcasts for a couple decades.
"His legacy continues to live on," Roberts said. "He was a friend of mine, and so to not see him up in the booth or to say hello is sad for me and his family. But Fernando was a gentleman, a great Dodger, and what a humble man."
Valenzuela was remembered around Dodger Stadium in a new mural on a wall near left field and with floral arrangements as well as blue ribbons near his framed jersey and Silver Slugger awards in the hallway outside the Dodgers' clubhouse.
A six-time All-Star, Valenzuela was 173-153 in 17 seasons, including 141-116 with the Dodgers from 1980-90.
The Associated Press contributed to this report.