With the 1970s behind him, Ron Burgundy, San Diego's former top-rated newsreader, returns to take New York City's first twenty-four-hour news channel by storm.

Gregorio and Ingrid Cortez are rival spies who fall in love. They retire and have two children, 12-year-old Carmen and 9-year-old Juni. They work for the Organization of Super Spies (OSS) doing desk work. The children have no idea of their parents' previous career. Gregorio and Ingrid are called back into the field when agents go missing. The children are left in the care of their uncle Felix. Gregorio suspects that children's television host Fegan Floop has kidnapped the agents and mutated them into his "Fooglies," creatures on his show.

Two years after the events of the first film, Larry Daley, former night guard at the American Museum of Natural History, now runs his own direct response television company that sells inventions based on his experiences. He travels to the museum, discovering most of the exhibits will be moved to the Federal Archives at the Smithsonian Institution and replaced with holographic information providers. The Tablet of Ahkmenrah is to remain in the museum, leaving most of the exhibits without the ability to come to life at night. After the exhibits are moved, Larry receives a phone call from Jedediah, who informs him that Dexter the monkey stole the tablet and took it to the Smithsonian, bringing every exhibit in it to life. Larry travels to Washington, DC, navigating his way to the archives with help from his son Nick while posing as a night guard.

Mal struggles with her new celebrity life as the girlfriend of King Ben, putting a spell on her hair making it blonde, and maintaining a princess-like personality that she is uncomfortable with. She admits her issues to her friends Evie, Carlos, and Jay, but they are content with their new lives in Auradon and do not wish to return to the Isle of the Lost. Evie scolds Mal for relying on her mother's spell book to solve her issues. Carlos, wishing to ask Jane to the upcoming Cotillion dance, turns to Mal for help to be honest with her. Mal gives him a sweet that will make him speak the truth, but his dog Dude eats it, magically speaking the truth in English and very frankly as a result.

A few decades after her original visit, Mary Poppins, the magical nanny, returns to help the Banks siblings and Michael's children through a difficult time in their lives.

The film opens outside of a building where Terrorism are holding hostages and a nuclear bomb. The Reno Sheriff's Department arrives in a helicopter, called in as experts. As the group prepare to deal with the situation, Deputy Travis Junior wakes up and realizes it was a dream; he was sleeping at the wheel and the vehicle he and Lt. Dangle are in crashes.