Katie Brown learns how difficult middle school can be when her best friend ditches her for the Popular Girls Club, but she manages to find a great new group of friends and together they form their own cupcake club.
All of Katie's friends in the Cupcake Club have outside interests, so Katie sets out to find an extracurricular activity, but when she makes the softball team, Katie realizes that team sports are harder than she expected.
The girls in the Cupcake Club are ecstatic when Mia asks them to be junior bridesmaids in her mother's wedding and they find the perfect dress, but while trying to pay for the dress without the help of her parents, Emma must balance babysitting her brother, a dog-walking business, flute practice, and baking for the Cupcake Club.
Alexis is excited about the Cupcake Club job for the neighbor's BBQ/pool party because her crush, Matt will be there. Unfortunately, things don't go according to plan with a big test she can't concentrate on and nothing to wear. Alexis's big sister, Dylan, comes to the rescue.
Emma got hit in the nose by a football by Jake who was showing off his throwing skills. Emma was counting on a modeling job to help pay for holiday gifts. The rest of the Cupcake Club reminds her that the best gifts come from the heart.
Mia struggles to be nice to the new girl, Olivia Allen, after she makes pains to be nice and loans her some money only to discover that Olivia spends it to buy the exact same shoes Mia has been saving for.
Alexis wonders since the leader of the Popular Girls Club has moved away Callie might want to be friends again, but then Callie announces that the Popular Girls Club is baking cupcakes for the school fund-raiser.
Alexis Becker, who handles the financial and organizational side of the Cupcake Club, decides to take a break from her responsibilities and really wants to ask Matt to be her date to the pep rally parade.
Mia enters a design-a-dress contest without knowing just how much work designing and sewing a dress could be. Things get eve worse when she tries to finish her creation during a Halloween cupcake party.
When Katie learns her mother's new boyfriend is her math teacher, Mr. Green, Katie is accused of getting special treatment in class, and it's the Cupcake Club to the rescue to help Katie deal with the rumors and the changes in her life.
Mia is still getting used to having her new stepdad and stepbrother around when she begins to struggle with writing in her Spanish class, and since her family, who speaks Spanish, is willing to help, Mia learns that she is lucky to have three parents.
Feeling like a third wheel in the Cupcake Club when best friend Emma goes away on a family trip, Alexis bonds with Katie while Mia spends time with a visitor, a situation that helps all the girls discover the benefits of sharing friendships with multiple people.