The massacre in the Stirlingshire town shocked the nation and led to the UK enforcing some of the strictest firearms legislation in the world.
Sixteen young children and teacher Gwen Mayor were murdered by gunman Thomas Hamilton, who opened fire on a gym class at Dunblane Primary School on March 13 1996.
No official events are being held to mark the 20th anniversary but tributes are expected to be paid at traditional church services in the town.
Modertor of the Free Church of Scotland, Revd David Robertson, told Premier he was praying for everyone involved.
He said: "Those who are still affected by it, particularly parents and siblings and so on, that they would continue to know healing. That the country as a whole learns from it."
The children who died were Victoria Clydesdale, Emma Crozier, Melissa Currie, Charlotte Dunn, Kevin Hassell, Ross Irvine, David Kerr, Mhairi MacBeath, Brett McKinnon, Abigal McLennan, Emily Morton, Sophie North, John Petrie, Joanna Ross, Hannah Scott and Megan Turner.
The legacy of the tragedy that unfolded in Dunblane two decades ago is gun legislation that is often described as some of the toughest in the world.
Revulsion at his actions resulted in nearly 23,000 firearms and 700,000 rounds of ammunition being handed in during a national amnesty in the months that followed.
The Firearms (Amendment) Act 1997 was introduced early that year, banning handguns greater than .22 calibre.
When Tony Blair swept to power in May, Labour introduced the Firearms (Amendment) (No. 2) Act 1997, which banned the private possession of almost all handguns regardless of calibre.