Seven years after the first film, Mavis (Selena Gomez) and her new fiancé Johnny (Andy Samberg) are finally married, with the approval of her father Dracula (Adam Sandler), and the world becomes aware of (and unfazed by) the existence of monsters. Mavis later reveals to Drac that she is pregnant and a year later, she gives birth to a baby boy named Dennis (Asher Blinkoff), who later befriends Wayne’s daughter Winnie (Sadie Sandler). Nearing his fifth birthday, Dennis has yet to grow his fangs and Drac worries that his grandson might not gain vampire powers. Noticing the dangers of Transylvania, Mavis starts to consider raising Dennis where Johnny grew up, much to Drac’s disapproval.
Drac tells Johnny (who does not want to leave the hotel either) to bring Mavis to California to visit his parents, Mike (Nick Offerman) and Linda (Megan Mullally), but to make sure to keep her distracted so that she will not move, leaving Drac to “babysit” Dennis. Drac enlists his friends, Frank (Kevin James), Wayne the Werewolf (Steve Buscemi), Griffin the Invisible Man (David Spade), Murray the Mummy (Keegan-Michael Key) and Blobby the Blob (Jonny Solomon) to help train Dennis to become a monster, to no avail.
Drac takes Dennis to his childhood summer camp, Camp Winnepacaca, where he learned to hone his vampire abilities and discovers that the camp is safer than it was when he went there. Drac stubbornly believes Dennis is a “late fanger”, so he hurls Dennis from a tall, unstable tower to pressure the boy’s transformation into a bat. Dennis does not transform, and Dracula has to fly and rescue him at the last second. The stunt is filmed by the campers and uploaded to the Internet, which eventually reaches Mavis and Johnny.