Act One

We meet Jenna, a waitress, as she's engrossed in the process of making a pie at the diner where she works ("What's Inside"). Her two friends (and fellow waitresses), Becky and Dawn enter as they get started with their day at work, just like they always do ("Opening Up"). Jenna is taking an order from Joe, a loveable curmudgeon, when she's overcome with nausea. She rushes to the bathroom, where Becky and Dawn follow her. Becky hands Jenna a pregnancy test and tells her that she needs to face the music and take the test ("The Negative"). The results prove Jenna's worst fear: she's pregnant. To cope with the panic, Jenna creates a recipe for Betrayed By My Eggs Pie.

Earl, Jenna's husband, enters the diner — and takes Jenna's tips, as he normally does. When Jenna tells Earl how quickly one of her pies sold out, he tells her not to get any lofty ideas and that she's "no Sara Lee". Jenna retreats into her mind to create My Husband's A Jerk Chicken Pot Pie. Earl leaves, and Becky tells Jenna that he isn't worth staying married to. Jenna explains that he's just had a tough time lately and that she can't afford to leave him anyway. Jenna gets back to work, finding an escape from her troubles through baking ("What Baking Can Do").

Jenna is in the waiting room at her doctor's office. An imaginary trio of pregnant women sing to her ("Club Knocked Up"). Jenna meets Dr. Pomatter, a young doctor who is new in town. She had expected to see Dr. Perkins, who had been her doctor her whole life. They have an awkward introduction, and as Jenna leaves the appointment, she hands him a pie she originally made for Dr. Perkins. Dr. Pomatter takes a bite and is blown away ("Pomatter Pie").

Jenna is working another day at the diner. Cal, the boss and cook, scolds all the waitresses for being late. Becky and Dawn surprise Jenna with a book for expectant mothers, and show her the suggestion in the book about writing a letter to her baby. Dawn reads her online dating profile to Becky and Jenna, who encourages her to post it that night. Dawn is worried that meeting someone will be a disaster ("When He Sees Me").

Joe enters. It's revealed that he owns the diner, Joe's Pie Diner — and many other businesses in town. Joe senses that Jenna is pregnant, and she begs him to not tell anyone. He changes the subject to the National Pie Bake Off that's happening nearby and nudges Jenna to enter. The $20,000 prize makes her consider it.

As Jenna waits for the bus to go home, she invents pies in her head. Dr. Pomatter shows up at the bus stop. He tells Jenna how she reminds him of another woman who worked at a bakery he loved ("It Only Takes a Taste"). This woman used to make the best pies — but Jenna's are far better. Jenna is clearly touched by his kindness and attention.

Not long after she gets home, Earl comes home with beer and a ton of rage. He was fired for constantly being late. Jenna turns down his advances and his demand that she "take my bad day away". This infuriates Earl and just as he's about to hit her, Jenna blurts out that she's pregnant. Earl is overjoyed but also makes Jenna promise that she won't love the baby more than him ("You Will Still Be Mine").

Back at the diner, Dawn has scheduled a date and is freaking out. Jenna agrees to make a Meet Your Dream Chocolate Cream Pie for the date. She tells Becky and Dawn that she's going to do the pie bake off and use the prize money to leave Earl. The three of them contemplate their dreams ("A Soft Place to Land"). Jenna starts hiding some of her tips from Earl.

Ogie, Dawn's persistent suitor, comes to the diner and insists on seeing Dawn. Dawn tells Becky and Jenna about their date and how peculiar he is. Dawn tells Ogie to leave her alone, but he declares they're meant to be together ("Never Ever Getting Rid of Me"). Dawn agrees to another date and is then impressed that he wants to take her to a reading of the Federalist Papers, and that he was in Revolutionary War re-enactments. Dawn begins falling for Ogie. Watching them, Jenna makes Almost Makes You Believe Again Pie. She calls Dr. Pomatter about some bleeding and makes an appointment.

Jenna arrives at Dr. Pomatter's office for a 7 AM appointment. Dr. Pomatter tells her that everything is fine for early pregnancy. Jenna demands to know why he had her come in early, before the office opens, to tell her that, and Dr. Pomatter can't give her a direct answer. Jenna storms out, only to come back to get her purse and kiss him. They both agree that since they're both married and Jenna's pregnant, acting on their feelings would be a "Bad Idea". They give in to temptation anyway.

Act Two

Jenna is at the diner coming up with new pies when she catches Becky and Cal kissing. Jenna asks Becky how she can cheat on her elderly husband, but Becky won't let Jenna judge and shame her, especially when she knows Jenna is sneaking around herself, and says indulging her feelings can be a good thing ("I Didn't Plan It").

Jenna goes to Dr. Pomotter's office a month after their kiss. He asks her to not spend a month without contacting him again. They kiss again, and their affair continues ("Bad Idea – Reprise"). At the diner, Joe immediately can tell Jenna is having an affair and lectures her on why it's not a good idea. Meanwhile, Dawn is having a passionate relationship with Ogie.

Jenna goes in for a doctor's appointment, only to learn he had to leave town with his wife for a wedding. Jenna listens to her baby's heartbeat and imagines her letter to her baby.

Dr. Pomatter surprises Jenna at work. She tells him she can't live with herself if they keep seeing each other. He surprises her with a golden pie plate and asks her to make a pie with him. As they do, he tells Jenna about the impact she's had on him ("You Matter to Me").

At Ogie and Dawn's wedding, Ogie composes a poem on the spot ("I Love You Like a Table"). At the reception, Joe dances with Jenna and gives her advice about going for what she wants in life ("Take It From an Old Man"). Earl enters in a fury and makes Jenna leave. He brings her home and shows her that he's found all the money she's hidden. Jenna lies, telling him that she was saving it to buy a crib and toys for the baby. Earl takes all the money. Jenna, crushed, imagines another letter to the baby ("Dear Baby") and explains she won't be able to make it to the pie bake-off. Jenna thinks about the kind of person she once was and how her life has disappointed her ("She Used to Be Mine"). Jenna begins to go into labor ("Contraction Ballet").

In the hospital, Jenna is in agony. Joe is wheeled into her room. He's about to have surgery but wanted to hand her a card first. Earl enters, ready to film the baby's birth. A group of hospital residents come to observe and one of them introduces herself as Francine, Dr. Pomatter's wife. Jenna is mortified. The residents leave, and Jenna gives birth to a girl. Jenna holds her daughter for the first time and is immediately in love ("What's Inside – Reprise"). She tells Earl she's leaving him and to get out. He leaves, and she is free ("Everything Changes – Part I"). Dr. Pomatter checks in on her, and Jenna tells him that meeting his wife has made her realize that the affair needs to end now. He agrees, and they thank each other for changing their lives. Jenna marvels at her daughter and names her Lulu ("Everything Changes – Part II"). Jenna opens the card Joe gave her and learns that she is inheriting the diner. She realizes he hadn't expected to survive the surgery. In the note, he asked her to name a pie after him.

Years pass. We're back at the diner where tons and tons of pies are being boxed up for orders. Lulu is now a little girl, and Jenna is running a business with the support of her diner family. The day is starting at the re-named diner, Lulu's Pies, and everyone's lives are moving forward ("Opening Up – Finale").