The adventure picks up where the previous film left off, with Alex (Ben Stiller) experiencing a nightmare about himself and his friends, who are unfortunately aging while stranded in Africa. Upon waking from this unsettling dream on his birthday, the animals surprise him with a delightful miniature model of New York City. Inspired, Alex proposes an escapade to Monte Carlo to enlist the penguins to help them return to their hometown. Joined by Marty (Chris Rock), Melman (David Schwimmer), and Gloria (Jada Pinkett Smith), they eagerly agree to this adventurous plan.
In Monte Carlo, the penguins and two chimpanzees, Mason and Phil, cleverly disguised as the King of Versailles, rack up gambling wins. However, when Alex and the gang’s clumsy efforts to reach the penguins lead to mayhem at the luxurious Hotel De Paris, it draws the attention of Captain Chantel DuBois (Frances McDormand), a tenacious Monaco Animal Control officer. Instead of capturing them alive, DuBois is intent on obtaining trophies — particularly Alex's head. What ensues is a wild high-speed chase involving the animals narrowly escaping, all while being pursued in a truck driven by the cunning penguins toward their aircraft from the previous film.
As the drama unfolds in the skies over France, engine failures cause the plane to crash into a suburban rail yard, sending the animals on a frantic quest for safety. They soon encounter a circus train, and upon seeing Gia, a beautiful jaguar ([Jessica Chastain]), Alex is instantly smitten. Claiming to be circus animals, they manage to board the train with the help of Stefano, a friendly sea lion ([Martin Short]), despite strong objections from Vitaly, a proud tiger ([Bryan Cranston]).
The animals soon discover they have ended up in a performing circus that is bound for Rome and London, where they hope to impress a promoter for a chance at an American tour. But as they prepare for their acting debut, it becomes clear that the circus performance is dismal – causing the audience to demand refunds and chase the troupe away. Disheartened by their failures, the group begins to rethink their strategy.
However, Alex finds inspiration in Vitaly's story, having once been a celebrated act that fell from grace due to a devastating accident. Using this motivation, Alex leads his friends to reinvent their performance styles into an animal-only circus, leaving behind the human acts of Cirque Du Soleil. This creative collaboration brings the animals closer, especially Alex and Gia, who find themselves falling in love.
Meanwhile, Captain DuBois, who has been arrested, breaks free and discovers Alex's identity through online research. This sparks her determination to pursue him once more. While the troupe prepares for their most important show, tensions rise as Vitaly plans to leave, believing himself to be a failure. However, Alex successfully convinces him to find confidence again, leading to a spectacular performance that dazzles the audience and secures an American tour.
Despite the newfound success, DuBois threatens to ruin everything, and when the truth about Alex's identity comes to light, it risks shattering the fragile bonds formed with their circus companions. Yet, when the circus troupe arrives in New York City, they are willing to forgive; realizing the friendships formed during their adventures are invaluable.
In a twist of fate, however, Alex and his friends are tranquilized and captured by DuBois. As the zoo staff celebrates Alex's return, misunderstandings persist. In a remarkable display of loyalty, Gia and Vitaly rally the circus animals to rescue their captured friends, executing an elaborate plan dubbed "Operation: Afro Circus Rescue."
With the help of the circus performers, Alex and his friends courageously confront DuBois, thwarting her attempts to harm them and proving the strength of their friendship. In the end, they decide to leave the confines of the zoo behind and embrace a new life with the circus as they embark on their much-anticipated American tour. Meanwhile, in a comedic twist, DuBois finds herself in an unwillingly similar situation as Alex, as she and her team are inadvertently shipped off to Madagascar.
