One woman was told it would take place from 7pm.
A fake website advertising a Halloween parade in Dublin city centre tricked thousands of people into turning up last night.
Gardaí had to ask people to move on after they lined O'Connell Street in anticipation of the event.
The website had promised a parade running from Parnell Square to Temple Bar.
This woman was told it would take place from 7 to 9 o'clock: