Ippei Mizuhara, who is known as a close friend of Ohtani, is alleged to have stolen money from the Japanese ace to place bets with a suspected illegal bookmaker.
"The Dodgers are aware of media reports and are gathering information," a Dodgers spokesperson wrote in an email to AFP.
"The team can confirm that interpreter Ippei Mizuhara has been terminated. The team has no further comment at this time."
The Los Angeles Times reported that West Hollywood law firm Berk Brettler LLP had looked into Mizuhara's actions after the newspaper learned that Ohtani's name had surfaced in a federal investigation of alleged illegal bookmaker Mathew Bowyer.
"In the course of responding to recent media inquiries, we discovered that Shohei has been the victim of a massive theft and we are turning the matter over to the authorities," Berk Brettler said in a statement.
The LA Times, citing two anonymous sources, said the money involved "was in the millions of dollars" and Mizuhara used it to place bets with Bowyer's operation.
ESPN reported questions had arisen around "at least $4.5 million (£3.5 million) in wire transfers sent from Ohtani's bank account" to an associate of Bowyer.
ESPN said that multiple sources, including Mizuhara himself, told ESPN that Ohtani doesn't gamble and that the funds covered Mizuhara's losses.
Major League Baseball's gambling policy bars "any player, umpire, or Club or League official or employee" from betting on baseball or making illegal bets on any other sport.
While sports betting has been legalized in a majority of US states, online betting and retail sportsbooks remain illegal in California.
Close companion
Japan's Ohtani, who has been likened to a modern-day version of Babe Ruth, joined the Dodgers in December in a 10-year deal worth $700 million after playing six Major League Baseball seasons with the Los Angeles Angels.
He is with the Dodgers in Seoul for a season-opening series against the San Diego Padres.
According to the Times, federal agents raided Bowyer's Orange County, California, home last year.
He has not been charged with a crime, although the Times reported that Bowyer has appeared in previous court filings and had a $1.75 million (£1.4 million) judgment against him for defaulting on a line of credit issued to him by a Connecticut casino.
Diane Bass, a lawyer for Bowyer, told the newspaper that he "never met, spoke with, or texted, or had contact in any way with Shohei Ohtani".
Mizuhara, who was born in Japan but was brought up in Southern California, became Ohtani's personal interpreter when he signed with the Angels in 2017 and followed him to the Dodgers.
He has been a close companion of Ohtani, who has emerged as the global face of MLB.
Ohtani's revelation in February that he had married captivated Japan, and his every move this week in South Korea has been headline news.
As Ohtani's star has risen, Mizuhara has been by his side, the two often arriving together at the ballpark for games and training and spending time together away from team facilities as well.
Mizuhara got his first job in baseball with the Boston Red Sox, interpreting for Japanese pitcher Hideki Okajima after graduating from college in 2007.
He returned to Japan to work for the Hokkaido Nippon Ham Fighters in 2013 and met Ohtani, who joined the club from high school the same year.
Mizuhara is well-known in Japan and news of his dismissal was met with shock around the country, with his name trending on X.
"I liked Ippei-san even before he became Ohtani's translator. Seriously, gambling?" one user wrote.
Another said the news was "a little hard to believe, because of the way he appears on the bench with Ohtani".
