Because of Winn-Dixie is a story of a young girl, Opal, and the summer when she grows up and stops feeling lonely and unloved. Opal and her dad, the Preacher, have moved to a small town in Florida called Naomi. Opal has no friends. And, to make matters worse, her mother deserted Opal and her father years ago, leaving Opal with a sad, empty place in her heart. Her dad doesn't like to talk about Opal's mother. However, Opal asks her dad to tell her ten things about her mother. One of those very important things the Preacher tells Opal is that her mom loved her very much.

During the course of the story, Opal rescues the dog she finds in the Winn-Dixie supermarket and names him Winn-Dixie. Because of Winn-Dixie, she makes friends in the town. Because of Winn-Dixie, Opal and her father cry over the loss of her mother, and he tells Opal her mom will never return. However, the Preacher also tells Opal that she is the best gift he could ever have. Because of Winn-Dixie, Opal realizes she is loved very much. The story ends happily with Opal, her father, and Winn-Dixie united as a family.

This story takes place over just a very few weeks one summer.  The main character, India Opal Buloni (usually called Opal) has moved to Naomi, Florida with her father (usually called the Preacher).  Opal is sad (partly because her mother left them long ago) and lonely.

One day, Opal finds this dog and makes him her own.  She calls him Winn-Dixie.  The dog helps to break the ice with the people of Naomi such as Miss Franny Block and Gloria Dump.  Because she has the dog, she gets to meet more people and gets to be less lonely.  She also is able to start talking to her father about her mother and gets to feel like she knows her mom a bit.

Her mom does not come back.  Winn-Dixie does not die.