Aberdeen lifeboat was launched on Wednesday evening following a report of a red flare south of the city.
A search was carried out of an area between Portlethen and Newtonhill, up to half a mile off the coast.
Nothing was found and the lifeboat was stood down.
Operations manager Bill Deans said: “In view of the date, it seems likely this was a false alarm sparked by fireworks.
“We would ask the public, aside from organised public displays, not to let off fireworks on the coast where they might be mistaken for distress flares and cause false alarms for the search and rescue agencies.”