Ippei Mizuhara, 39, will plead guilty to one count of bank fraud - punishable by up to 30 years in prison - and one count of filing a false tax return, which carries a maximum sentence of three years, the Justice Department said.
Federal prosecutors have said Mizuhara - Ohtani's long-time friend and confidant - plundered millions from the Los Angeles Dodgers ace's bank account to fund an "insatiable appetite" for gambling.
Mizuhara is expected to formally enter his guilty plea in the coming weeks, with arraignment scheduled to take place in Los Angeles on May 14.
"The extent of this defendant's deception and theft is massive," United States Attorney Martin Estrada said in a statement on Wednesday.
"He took advantage of his position of trust to take advantage of Mr Ohtani and fuel a dangerous gambling habit," Estrada added.
Japanese sensation Ohtani, currently the biggest star in baseball, joined the Dodgers last December in a record-breaking $700 million deal (£560m) - the richest contract in North American sports history.
Tyler Hatcher, special agent in charge from the Internal Revenue Service's criminal investigation unit, said the probe had revealed Mizuhara "not only stole from Mr Ohtani, but also that he lied to the IRS about his income."
"Mr Mizuhara exploited his relationship with Mr Ohtani to bankroll his own irresponsibility," Hatcher said in a statement.
Mizuhara's guilty plea had been expected.
After an initial court appearance last month, his lawyer said he wished to apologise to "Ohtani, the Dodgers, and Major League Baseball" for his actions and sought a swift resolution so he can "take responsibility."
Massive losses
The revelations surrounding Mizuhara erupted as the new baseball season got under way in March, stunning the sports world and potentially embroiling Ohtani in scandal.
Prosecutors have repeatedly emphasized that Ohtani was an innocent victim of Mizuhara's deception, and that there was no evidence to suggest the Dodgers star was aware of or involved in illegal gambling.
A criminal complaint released by prosecutors last month detailed a staggering volume of bets placed by Mizuhara, who exploited the language barrier to keep Ohtani, his financial advisors and management team in the dark about his crimes.
The complaint revealed that between December 2021 and January 2024, Mizuhara placed approximately 19,000 bets ranging in value from $10 to $160,000 (£128k) at an average of around $12,800 (£10.2k) per bet.
During that period, Mizuhara had winning bets worth $142.3 million (£114m), and losing bets of $182.9 million (£146.4m) - leaving him with losses of roughly $40.7 million (£32.6m).
The complaint detailed that contact information on Ohtani's bank account was later changed to link it to Mizuhara's phone number and to an anonymous email address connected to Mizuhara.
Mizuhara also would allegedly falsely identify himself as Ohtani to trick bank employees into authorizing wire transfers.
Bank recordings of telephone calls captured Mizuhara impersonating Ohtani as he sought to make wire transfers.
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.
Players found guilty of betting on a game they were involved in are subject to life bans, with one-year suspensions if they are found to have gambled on games they are not directly involved in.
Ohtani is a rarity in baseball in that he combines elite-level pitching and hitting ability, making him a generational talent who has been portrayed as a modern-day version of Babe Ruth.
Those skills and his clean-cut image have made him the global face of baseball.
Ohtani is currently leading baseball's key hitting rankings, with an MLB-leading average of .358 as well as an MLB-best 11 home runs.
