Gravesham Borough Council said it had taken the step after consulting over the welfare of the arctic mammal, dubbed Benny, which was seen off Shorne Marshes in Gravesend last month.
In a statement, the council said: “The environmental advice on the effects of fireworks on or over the river is that the fireworks would cause disturbance to Benny.”
Council leader David Turner said the authority wanted to “ensure our special visitor is kept safe and well”.
“While we are very disappointed at having to postpone the fireworks, we understand the need to keep Benny safe must take priority,” he added.
Image: The beluga whale was seen in the River Thames close to Gravesend
Benny was first spotted in Gravesend on 25 September, and has since been seen swimming strongly and feeding normally.
The council‘s statement said the whale “looks set to stay as he feels right at home”.
Image: Gravesham Council said it was considering the safety of the 'special visitor'
The authority has been advised that disturbing the whale would be a breach of the Wildlife and Countryside Act, it added.
It is a rare visit for the beluga, a species that usually inhabits the coastlines of northern Scandinavia, Russia, Alaska and Canada.
The council has urged people to think twice about holding private firework displays near the river in Gravesend.
As part of the campaign to protect the whale, the authority is using the #KeepBennySafe and promises the fireworks will be rearranged when Benny leaves.