But Senate Ethics Officer Lyse Ricard said no sanctions will be imposed on the Quebec Conservative senator because he committed errors of judgment "in good faith."
The report said Boisvenu hired Isabelle Lapointe as an executive assistant in 2010 and then developed a relationship with her.
The personal relationship was made public in March 2013, when it was discovered the senator asked for a housing allowance because he had lived at Lapointe's home since the summer of 2012.
Boisvenu reimbursed the Senate but his intermittent relationship with the woman continued to get wide media coverage because she continued to work in his office.
Sen. David Tkachuk, the chair of the Senate internal economy committee, suggested at the time that Lapointe obtain temporary work outside the Senate to give her time for find other employment.
But before starting her new job, Lapointe asked for two weeks of sick leave to get away from the media turmoil that she and her children had lived through.
The report says that after she ran into difficulties, Boisvenu personally intervened to make sure that she would get the leave.
But the ethics officer says that's where the senator acted in "an irregular manner."
Boisvenu has said that he did nothing wrong, maintaining that he acted as any employer would.
His office said Wednesday that Boisvenu was on vacation and not reachable.