Marc Leduc was arrested at the Ottawa-Carleton Detention Centre on Wednesday in connection with the deaths of Pamela Kosmack, 39, and Leeanne Lawson, 23, lawyer Ian Carter told CBC News.
The Ottawa man was already in police custody facing eight charges connected to an alleged sexual assault in early November at a west Ottawa apartment building.
In that case, he is accused of breaking into the apartment of a 19-year-old woman who was sleeping and sexually assaulting her while brandishing a knife.
Kosmack was found partially nude and beaten to death in June 2008 on a bike path near Lincoln Fields transit station in west Ottawa. Police recently offered $50,000 for information that would help solve the five-year-old homicide of the woman who struggled with addictions.
Lawson was found dead in a parking lot in Ottawa's Lowertown neighbourhood in September 2011.
Accused to appear in court Thursday
Leduc is scheduled to appear in court Thursday morning at 9:30 a.m. ET.
Ottawa police Chief Charles Bordeleau is scheduled to hold a news conference at 11 a.m. ET Thursday regarding the charges.
Kosmack's brother-in-law, Darrin Murch, said Wednesday the news was a positive step for a family that has waited a long time for a suspect to be found.
"It's a bittersweet day," Murch told the CBC's Alistair Steele. "It's a good day that after four years, eight months and two days somebody's finally been charged with the murder.
"A great day would be never having to have this day in the first place. Our family is very happy. We're just trying to move on, and now my sister-in-law can rest in peace."
Police told CBC News more than a year ago they believed a suspect who killed multiple sex workers may be linked to the unsolved homicide of Kosmack.