Pro boxer Joseph "JoJo" Diaz -- a former champ who fought Devin Haney back in 2021 -- was arrested in the Los Angeles area on Monday ... TMZ Sports has learned.
Jail records show Diaz was taken into custody by the Claremont Police Dept. just before 7 PM Law enforcement sources tell us he was booked on a charge of misdemeanor child neglect.
The specific allegations against Diaz are still not clear ... but records show he was released on Tuesday afternoon.
The 30-year-old fighter holds a 32-3-1 pro record.