The clip from a 1916 Rising commemorative film shows Collins in a jovial mood at the wedding of General Seán Mac Eoin in June 1922.
It has been shown at schools and festivals for the past year, but is unseen by the public.
The video shows Collins, with Arthur Griffith to his right, joking with wedding guests as they are having their photo taken.
Three months after the clip, both men would be dead.
Many thanks to www.irelandbirthofanation.com for the footage.