Three years have passed since the events of Pitch Perfect 2, and now the Bellas have graduated from college, yet are stuck in jobs they detest. Yearning to reunite and perform together once more, Beca (Anna Kendrick), Fat Amy (Rebel Wilson), Chloe (Brittany Snow), Aubrey (Anna Camp), Lilly (Hana Mae Lee), Stacie (Alexis Knapp), Cynthia (Ester Dean), Flo (Chrissie Fit), Jessica (Kelley Jakle), and Ashley (Shelley Regner) are ecstatic to discover that Emily (Hailee Steinfeld), now a senior and the leader of the Barden Bellas, has invited them to a reunion at the New York Aquarium. However, upon their arrival, the women learn that the gathering is not for them to perform, but rather to watch Emily sing with the new generation of Bellas.
Disappointed, the group gathers at a bar where Emily apologizes, admitting she thought this was the only way to reunite. The heartfelt moment reveals how much they’ve missed each other. Suddenly, Aubrey proposes that they join a USO performance facilitated by her Army officer father, promising that if they win, they will have the chance to open for DJ Khaled. All the Bellas agree to participate, with the exception of Stacie, who is eight months pregnant and unable to join them.
The Bellas soon find themselves in a hangar, facing off against other musical groups, including the band Evermoist, led by Calamity (Ruby Rose). After Evermoist ridicules them, the Bellas challenge them to a riff-off but ultimately leave feeling defeated. Their journey takes them to a lavish hotel in Spain, where Chloe begins to develop feelings for Chicago (Matt Lanter). Meanwhile, Fat Amy discovers a nostalgic childhood toy that leads her to the unsettling realization that her father, Fergus (John Lithgow), an international criminal, is also staying at the hotel.
During a party at DJ Khaled's suite, Fat Amy connects with her father, who begs her to reintegrate him into her life. Though hesitant, she warms to him after witnessing his transformation. Simultaneously, Beca forges a bond with DJ Khaled's music producer, Theo ([Guy Burnett]), and impresses him with a mix she created, which he shares with DJ Khaled. However, the celebration takes a sudden turn when Aubrey accidentally causes a fire in the suite, leading to the Bellas facing disgrace and hopelessness.
Just when the tide seems to shift against them, Stacie delivers joyful news of the birth of a baby girl she named Bella, igniting a renewed passion in the Bellas to perform wholeheartedly, regardless of the competition outcome. At the USO competition, they deliver stunning performances that win over the crowd and help restore their reputation. However, during a confrontation with Fergus, Amy is heartbroken to discover he has ulterior motives for wanting to reconnect, as he only desires her mother’s money.
Beca, having been personally invited by DJ Khaled to open for him, decides to decline the offer, feeling conflicted about her place in the competition. Meanwhile, an ominous twist occurs as the Bellas are kidnapped and brought to Fergus’s yacht. In a daring rescue, Beca distracts Fergus with a performance while Amy sets the yacht to explode, allowing the Bellas to escape just in time. Fergus survives but is subsequently arrested for his crimes.
After the military rescues the Bellas, Fat Amy reveals DJ Khaled’s offer to Beca, who is urged to seize the opportunity. The Bellas acknowledge that while they may be moving on with their lives—Fat Amy will use her funds for tributes, Chloe is accepted into vet school, Cynthia Rose pursues flight school, Emily returns to school to continue songwriting, and Lilly reveals her quiet nature was due to being possessed—they will always remain a family at heart.
In the end, Beca performs on stage opening for DJ Khaled, before inviting the Bellas to join her for their final performance. They sing "Freedom! '90" passionately, encapsulating the joy of their sisterhood. Gail (Elizabeth Banks) and John (John Michael Higgins), who have documented the Bellas’ journey, realize they failed to record the climax of the documentary. As the credits roll, glimpses of the Bellas’ new paths come to light: Lilly flirts with DJ Dragon Nutz, Chloe shares a moment with Chicago while Beca discusses her future with Theo, and Aubrey reconnects with her father, portraying a beautiful sense of closure for each character.
