Fallout 76 Halloween Event 2021 - Mischief Night
Fallout 76 did hold a Halloween event in 2019 called Mischief Night, but it didn't return in 2020.
This event offered up new quests and rewards to earn themed around the spooky occasion. A new public event was also added which offered up some treats.
As mentioned, this event didn't return in 2020, so it isn't clear if Fallout 76 will hold a Halloween event in 2021.
There is always a chance the team could come up with a new event or add some new activities, but we will likely get firm details about any Halloween plans for Fallout 76 in September or October.