Like his 1st Dimension counterpart, Ferb is intelligent but he rarely speaks. Other than that, little of his personality is revealed in the movie, although he most likely wants to join The Resistance in their mission to bring down Doofenshmirtz as much as Phineas does.
Ferb is physically identical to his 1st Dimension counterpart, with the exception that he is paler, has his hair cut military-style, and wears a white shirt and Dooferalls. As a Resistance member, he wears a black shirt, black pants, black boots, an Army-green jacket, black gloves, and black sunglasses.
Ferb and Phineas meet their 1st Dimension selves while playing Doofopoly, and he and Ferb-1 exchange handkerchiefs while watching Phineas hug Perry-1 under the impression that he is their Perry. After Perry-1 departs, the four go to Isabella's house; during the walk, they are saved by Buford from a patrolling Norm bot. The five then arrive at the Resistance headquarters via chute, and he and Phineas, along with Phineas-1 and Ferb-1, find out that Candace is the leader of the Resistance.
Candace agrees to aid Phineas-1, Ferb-1, and a recently-arrived Candace-1 in rescuing Perry-1, who was captured by Doofenshmirtz. However, he and Phineas are told to stay behind; despite this, they stow away in mine carts used by the Resistance. When Perry is rescued and an army of Norm bots pursues them as a result, Candace is forced to separate their minecart from that of the 1st Dimension characters' to save her brothers from certain capture.
After managing to become a Resistance member along with Phineas, Ferb aids Jeremy in his mission to rescue a captured Candace. She initially disapproves of her brothers' decisions, but after realizing that they can handle themselves in the outside world, she changes her opinions and shares a hug with the two of them.
Ferb is later amongst the Resistance members that travel to the 1st Dimension to congratulate the residents in defeating Doofenshmirtz. He and Phineas share a loving reunion with Perry, whose evil was "fried out of him" after a battle with Perry-1.
As revealed in "Tales from the Resistance: Back to the 2nd Dimension", Ferb settled down into a peaceful life with his family, feeling happy that Perry is now back. He and the other kids settled down, reinvigorating their sense of fun towards sports. However, the glee is cut short when Perry is kidnapped by several animal cyborgs (who happen to be the missing agents of O.W.C.A. during Doofenshmirtz's reign). Ferb later learns from Candace that Doofenshmirtz's wife Charlene was the one responsible for turning the agents into cyborgs and kidnapping Perry, Ferb aids the Resistance into rescuing Perry. However, he is followed by Pandaborg, who supposedly caught him and brought him to Charlene, who then turns Ferb into a cyborg. This allowed a freed Doofenshmirtz and Charlene to finally trap Candace, Phineas, and Perry in Charlene's penthouse. However, it turns out that Ferb had actually faked being turned into a cyborg and released his siblings and Perry, as part of their plan to launch a frontal attack on Charlene's penthouse. After the Resistance arrives in Charlene's penthouse, Ferb engages in a fight with Pandaborg. Fortunately, Perry manages to defeat Pandaborg by sending a pillar to fall on him, saving Ferb. Eventually, after the rest of the animal agents are freed from their evil programming, Candace is about to send both Doofenshmirtz and Charlene into custody, only to be interrupted by their daughter Vanessa, who convinces Candace to let her have a moment with her family. As Phineas and Ferb watch Vanessa sharing a moment with her family, Vanessa suddenly takes the opportunity to help her family and Pandaborg to escape in a hover car driven by Vanessa's boyfriend Tony Marzulo. Despite the Doofenshmirtz family's escape, Ferb would still continue settling down to a peaceful life with his family.
He only speaks one short line in the entire film, during the lyrics of "Summer (Where Do We Begin?)", compared to his 1st Dimension counterpart, who speaks a few more lines.
He apparently learned classical guitar off-screen.