Sixteen-year-old Juno MacGuff, portrayed by Elliot Page, finds herself facing an unexpected reality when she learns she is pregnant. The father is her friend and longtime crush, Paulie Bleeker. In a moment of youthful experimentation, they explored their feelings for one another while having a passionate encounter in her chair.
After confirming her pregnancy with the help of Rollo (Rainn Wilson), the convenience store clerk, Juno seeks advice from her best friend, Leah (Olivia Thirlby). They craft a plan to inform Paulie by placing the chair outside his house and breaking the news upon his morning jog. Shocked by the revelation, Paulie wants to know her next steps.
Initially, Juno considers the option of an abortion. She visits a local clinic run by a women's group, where her experience becomes disheartening as she faces an unfriendly environment and feels demeaned by the staff's terms. > "Sexually active" is a term she finds objectionable, and after feeling alienated, she makes the courageous decision to give the baby up for adoption instead.
With Leah's support, Juno turns to the Pennysaver, discovering a couple that seems to provide the perfect home. They agree to cover her medical expenses and have been yearning for a child for five years. Sharing her situation with her supportive father, Mac, and stepmother, Bren (Allison Janney), Juno finds the backing she needs. Mac's military background and Bren's love for dogs contrast her soon-to-be reality as she navigates pregnancy.
Juno meets the hopeful couple, Vanessa Loring and Mark (Jason Bateman), in their upscale home, where they agree on a closed adoption. Juno is firm in relinquishing her rights to the child, motivated by her desire to find a loving environment for her baby. Vanessa's sincere enthusiasm makes an impression on Juno.
As their relationship deepens, Juno connects with Mark over shared interests in punk rock and horror movies, leaving behind a glimpse of her former life. They discuss birth mother experiences, and Juno reassures Vanessa not to worry about her commitment to the adoption.
Juno's emotional journey intensifies when she witnesses Vanessa’s natural ease with children, motivating her to encourage Vanessa to bond with her unborn baby. However, the situation becomes complicated as Juno grapples with her feelings for Paulie, who openly loves her while preparing for prom plans that don't include her.
Tension erupts when Juno learns Paulie's feelings and plans. Ironically, as her baby’s due date approaches, Juno faces a pivotal moment when Mark reveals he wants to leave Vanessa, leading her to reevaluate her feelings for both Mark and Paulie. After witnessing the unraveling of Mark and Vanessa's relationship, Juno has a heartfelt talk with her father, coming to terms with her love for Paulie.
In a heartfelt culmination, she confesses her love to Paulie, which he returns. The climax occurs when Juno goes into labor, prompting a frantic rush to the hospital. Paulie, finding her missing from the stands, hurries to offer comfort after she gives birth to their son.
Vanessa joyfully arrives at the hospital to claim the newborn, and on the wall of the nursery, she frames a note from Juno: > "Vanessa: If you're still in, I'm still in. -Juno." In a heartwarming conclusion, Juno and Paulie are seen playing music together in the summertime, sealing their connection with a tender kiss.
