Wu married Michelle Maxine Wu in 1996 and they have two children. In December 2009, he filed for separation from his wife, citing irreconcilable differences.
Three weeks prior to the 2004 elections, The Oregonian published an article reporting that Wu had been accused of sexually assaulting an ex-girlfriend while attending Stanford. Stanford made Wu attend counseling and was disciplined by the university in 1976. Criminal charges were never filed, but the story prompted Wu to hold a press conference apologizing for "inexcusable behavior".
In February 2011, Willamette Week and later The Oregonian reported that in the runup to the November 2010 election, Wu began behaving erratically and that staffers "demanded he enter a hospital for psychiatric treatment." The erratic behavior that triggered the staff's departure was reported to be no single incident but rather a pattern of behavior that included Wu's emailing his staff photos of himself in a tiger suit.
After Wu won re-election, at least six of his staffers left, including his longtime chief of staff and his communications director. In a statement, Wu acknowledged he has sought "professional medical care" and attributed the problems to the stress of being a single father, the death of his father, and his political campaign. The Oregonian has reported that a campaign contributor gave Wu a prescription painkiller, identified by the staffer present as oxycodone to help alleviate an episode of severe neck pain. Willamette Week quoted the donor as saying the pills were ibuprofen. Wu has admitted taking the painkiller, saying that it was an act of bad judgment, but claiming that he does not know what it was.
On July 22, 2011, The Oregonian reported that a teenager accused Wu of an aggressive, unwanted sexual encounter. The teenager is the daughter of a longtime friend and campaign donor. Wu admitted the encounter, but said it was consensual.