The deal is reportedly for one year.
The story was first reported by ESPN's Chris Mortensen.
McDonald was released by the 49ers in December after he was accused of sexual assault. This marked the second time in four months that McDonald was linked to a domestic violence related incident.
McDonald recently told ESPN he is planning to sue the accuser in the most recent sexual assault claim. He was not charged in the first investigation due to insufficient evidence, according to the Santa Clara District Attorney's office.
By joining the Bears, McDonald will reunite with defensive coordinator Vic Fangio.
"I feel like what I am doing is the right thing because I know that I am not this bad person that people are making me out to be," McDonald told ESPN on Monday. "I've been fired from my job. I know some teams don't even want to talk to me because of this past accusation. All I am trying to do is clear my name and move on with my life."
The 49ers released McDonald in December citing "a pattern of poor decision-making."
His attorney, Steve M. DeFelippis, said in a statement that the "unresolved threat of charges being filed against him, even though factually unfounded, continues to present a roadblock to this remarkable athlete being able to move forward in his career. This lawsuit is intended to vindicate him ... and return his good name."
McDonald, 30, played in 14 games last season, recording 39 tackles, three sacks and a forced fumble.
While his agent said the allegations are closed, the Santa Clara County District Attorney's office said in a statement that they are still reviewing the matter, reports The Sacramento Bee. McDonald is facing a sexual assault allegation.
"The District Attorney's office has made no decision on the most recent Ray McDonald matter," according to the statement. "When the investigation is complete, this office will release our findings publicly or through publicly filed charges."
The team had stood by McDonald after the first incident, but apparently have lost faith in his innocence.
McDonald, who was finishing his eighth season with San Francisco and has started every game this year, ends 2014 with three sacks and having contributed to 39 tackles.
San Jose Police are investigating after a woman claimed
McDonald has not been arrested.
McDonald was investigated in a domestic violence case following an Aug. 31 fight with his pregnant fiancee, but the District Attorney's office did not file charges, "citing insufficient evidence, and said it appeared the fiancee initiated the physical contact."
The 49ers stood by McDonald in that incident, and he has started every game this season.
|2007||San Francisco 49ers||9||3||3.0||0||1||0||0||0.0||0||0||0|
|2008||San Francisco 49ers||15||27||20.0||7||1||0||0||0.0||0||0||4|
|2009||San Francisco 49ers||16||8||6.0||2||3||0||0||0.0||0||0||0|
|2010||San Francisco 49ers||16||19||13.0||6||0||1||31||31.0||31||1||2|
|2011||San Francisco 49ers||15||39||29.0||10||5.5||0||0||0.0||0||0||2|
|2012||San Francisco 49ers||16||38||28.0||10||2.5||0||0||0.0||0||0||1|
|2013||San Francisco 49ers||14||37||29.0||8||3.5||0||0||0.0||0||0||1|
|2014||San Francisco 49ers||14||39||25.0||14||3||0||0||0.0||0||0||0|
|Year||Team||G||Fum||Lost||Fum Forced||Own Rec||Opp Rec||Yds||Tot Rec||TD|
|2007||San Francisco 49ers||9||0||0||0||0||0||0||0||0|
|2008||San Francisco 49ers||15||0||0||0||0||0||0||0||0|
|2009||San Francisco 49ers||16||0||0||0||0||2||11||2||1|
|2010||San Francisco 49ers||16||0||0||0||0||0||0||0||0|
|2011||San Francisco 49ers||15||0||0||2||0||1||0||1||0|
|2012||San Francisco 49ers||16||0||0||1||0||0||0||0||0|
|2013||San Francisco 49ers||14||0||0||0||0||0||0||0||0|
|2014||San Francisco 49ers||14||0||0||1||0||0||0||0||0|
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