The film opens with Red, voiced by Jason Sudeikis, frantically running through the forest with an egg. He collides with trees and other animals before arriving at a bird family's home, where he dons a clown costume and attempts to sing to little Timmy on his hatch-day. However, Timmy is terrified of clowns. Timmy's father, voiced by Hannibal Buress, scolds Red for arriving late and ruining the cake he was meant to bring. In a fit of frustration, Red retaliates by smashing the cake in his face. While trying to escape the chaos, he accidentally cracks the family's new egg, making him the first sight for the hatchling.
Living on Bird Island, Red resides in a beachside house, isolated from other flightless birds. His childhood ridicule over his oversized eyebrows has left him friendless. He is soon put on trial by Timmy's family for his angry outburst. During the trial, Judge Peckinpah, voiced by Keegan-Michael Key, cites Red's anger issues, and in response, Red comically reveals himself standing atop another bird named Cyrus, voiced by Tony Hale. Consequently, Peckinpah orders Red to attend anger management classes.
Reluctantly, Red attends the class, where he encounters a signboard bird that annoys him. He chooses to ignore it until it hits him in the head, prompting him to retaliate violently. Inside the hut, he meets the teacher, Matilda, voiced by Maya Rudolph, and other misfit birds: Chuck, voiced by Josh Gad, known for his speed and mischief; Bomb, voiced by Danny McBride, who explodes under pressure; and Terence, voiced by Sean Penn, a massive bird that only grunts and is rumored to have a dark past. Despite their attempts at yoga, Bomb’s stress leads to yet another explosion.
As Red discovers more about his new friends, he is still reluctant to connect. In the next session, the birds are tasked with writing poetry, and Chuck's poem hints at Red's earlier mishap. Tensions escalate when the arrival of a strange ship disrupts their lives. It is Leonard, voiced by Bill Hader, a bearded pig from Piggy Island, who arrives with his assistant Ross (also voiced by Tony Hale). While Leonard claims he wishes to befriend the birds, Red distrusts his motives, resulting in a divide between him and the other birds, who are intrigued by Leonard's entertainment and games.
That night, a celebratory event for the pigs unfolds, featuring trampolines and slingshots—much to Red's displeasure. When Red and his friends, Chuck and Bomb, decide to sneak onto the pigs' ship, they uncover a shocking discovery: Leonard is hiding a hoard of pigs on board. Confronted by Red, Leonard insists they are his cousins; however, Red's suspicion only grows as he observes Leonard inching towards an egg.
Determined to understand the pigs better, Red, Chuck, and Bomb embark on a journey to find the legendary Mighty Eagle, believing he may help them protect the island. As they climb the mountain, they are met with disappointment when they finally discover that the revered Mighty Eagle, voiced by Peter Dinklage, is not the figure of strength they imagined.
The three birds, filled with renewed purpose, rush back to warn their fellow inhabitants only to find the pigs executing a nefarious plan to steal the eggs during a party. Determined to stop them, Red leads the charge, devising a plan to construct a boat and pursue the pigs back to Piggy Island to reclaim their stolen eggs.
Upon arriving, the birds use a giant slingshot to infiltrate the pig stronghold. As chaos ensues, Matilda showcases her explosive powers while Red, Chuck, and Bomb navigate the pig castle to rescue the eggs just before they're cooked. The climax pits Red against Leonard in a battle for the eggs’ fate, resulting in an explosive confrontation that destroys the pigs' fortress but ultimately leads to the salvation of the eggs.
In the aftermath, as the birds celebrate their hard-fought victory, they express their gratitude towards Red, who learns the value of friendship and community as they help rebuild his home in the heart of their village. Although he initially contemplates solitude, he eventually invites Chuck and Bomb in, marking the start of a newfound camaraderie.
As credits roll, the joyful festivities continue, revealing that the pigs, somehow unscathed, are devising their next scheme, and the Blues playfully launch themselves into the sky—a fitting end to an adventure-filled saga.
