Outgoing Prime Minister Stephen Harper and Prime Minister-designate Justin Trudeau - in their first appearance together since Monday's election - laid a wreath in remembrance.
Dignitaries were joined by a large crowd as well-armed police kept watch.
The attacks helped usher in a sweeping anti-terrorism law.
"We will not allow threats to shape us, nor bow to those who mean to undermine our values and way of life," Mr Trudeau said on Thursday at the National War Memorial in Ottawa.
One year ago, Michael Zehaf-Bibeau, a Muslim convert shot and killed Nathan Cirillo at the war memorial before attacking parliament.
Zehaf-Bibeau charged into parliament and fired several shots before he was killed by Parliament's Sergeant-at-Arms Kevin Vickers.
Another Canadian service member, Warrant Ofc Patrice Vincent, was killed in a separate attack only a few days before.
Canadians have gathered to pay tribute to an honour guard soldier -  a year after he was killed by a gunman who went on to storm parliament.