The annual conference, which began in 2009, brings together defence and international security experts from around the world to share ideas about the most pressing security challenges.
More than 300 delegates from 50 countries are expected to attend. Participants also include policy-makers, members of the international media, security analysts, diplomats and business leaders.
Defence Minister Rob Nicholson and U.S. Defense Secretary Chuck Hagel are among those scheduled to speak.
Nazanin Afshin-Jam, MacKay's wife and the president Stop Child Executions, is also expected to speak to the conference.
"For the next three days, the world stage will be right here in Halifax," MacKay told a news conference at a downtown hotel.
"The participants are here to connect, to collaborate and to discuss some of the key challenges of the global security horizon."
MacKay, the federal minister responsible for Nova Scotia, said the conference has earned a world-class reputation like that of the annual economic forum held in Davos, Switzerland.
Other topics up for discussion in Halifax include cyber crime, African security, the Middle East, Afghanistan, the Arctic and Iran's new approach to international relations.
Conference organizers, based in Washington, D.C., stress that the forum offers an informal, unscripted atmosphere to encourage open debate and discussion.
MacKay, a former defence minister and the member of Parliament for Central Nova, said just over $6 million in funding will come from the National Defence Department, with the rest coming from the Atlantic Canada Opportunities Agency.