Arturo Gatti's widow says the late boxer's family was aware of his substance abuse but she was largely alone in helping him.
Amanda Rodrigues says she helped check her husband into a rehabilitation facility in Florida in December 2007.
She says the boxer was abusing alcohol and painkillers.
But she says Mr. Gatti left rehab after about a week, with the help of his sister Anna Maria.
Ms. Rodrigues says she tried to help her husband with his addictions, but didn't know how.
As Ms. Rodrigues testifies today in a civil trial, negotiations are ongoing in the hope of settling a dispute over Mr. Gatti's $3.4-million estate.
The Gatti family and Rodrigues have been at odds since the boxer's 2009 death at a Brazilian resort.
The boxer's family does not accept the conclusion of Brazilian authorities that he committed suicide. And they reject the legitimacy of a will, signed just weeks before his death, that left everything to Ms. Rodrigues.
The Gatti family has said their preference is that the fortune be split equally between Mr. Gatti's child with Ms. Rodrigues and his child from a previous relationship. They say they don't want any of the money for themselves.