Ian Bush, 59, is already accused of attempted murder in last December's attack on a 101 year-old war veteran.
On Friday, police charged Bush with three counts of first-degree murder in the 2007 slayings of retired tax court judge Alban Garon, his wife Raymonde and their neighbour, Marie-Claire Beniskos, all in their 70s.
The victims were found beaten and tied up, with plastic bags over their heads, inside the Garons' 10th-floor condomium near the Rideau River.
The suspect is facing charges in another case from two months ago. Bush is accused in the home invasion robbery and attack on Ernest Côté, a Second World War veteran of the D-Day landings.
Côté was also left with a plastic bag over his head, although he managed to free himself and call police.
Police have not said much about what led them to Bush, but the say the evidence includes DNA.
"The investigation into the December home invasion prompted investigators to consider Bush as a suspect for the 2007
homicides," Ottawa Police Chief Jill Skinner said.
Bush has been in custody since police charged him with attempted murder in connection with the home invasion at Côté's second-floor apartment.