The man shouted about breaches of the Geneva Conventions on the conduct of war during Blair's years in office as the ex-leader took the stage.
"I wouldn't come any further... you can go," Blair said as the man approached the podium where he was standing.
The unidentified man, who spoke with a British accent, came within metres (feet) of the former prime minister before being blocked by university staff and escorted peacefully from the room.
"That's democracy for you," Blair said as the man was led away.
Blair went on with his speech apparently undeterred by the incident, telling his audience that the forces of globalisation were "multiplying and intensifying the impact of religion" around the world.
He said the world needed more "platforms of interfaith dialogue and action" to improve understanding between people of different belief systems.
Blair, who was Labour prime minister between 1997 and 2007, took Britain into the US-led war in Iraq in 2003, as well as sending troops into Afghanistan as part of the US-led operation in 2001.
He was appointed envoy for the Middle East Quartet comprising the United States, United Nations, European Union and Russia in 2007 but his role has come under increased scrutiny recently as efforts for peace have stalled.
He was speaking in Hong Kong as the founder of the Tony Blair Faith Foundation, which seeks to promote understanding between the major religions.
"The 20th century battle ... between left and right is gone," he said, adding that he believed the biggest threat to world peace in the 21st century was religious conflict.
"This issue cannot be minimised, it cannot be treated as anything other than it is, and it's got to be studied."