The family consists of Olive, a bright and optimistic 7-year-old girl who dreams of winning the Little Miss Sunshine pageant; her parents, Richard and Sheryl, who are struggling with their marriage and their own personal issues; Olive's grandpa, a foul-mouthed and heroin-addicted retired professor; Olive's uncle, Frank, a suicidal and gay Proust scholar; and Olive's older brother, Dwayne, a Nietzsche-loving teenager who has taken a vow of silence until he becomes a pilot.
As they drive from Albuquerque to Redondo Beach, the dysfunctional family encounters a series of obstacles and mishaps, including a broken clutch, an awkward encounter with a motorcycle cop, and a heartbreaking revelation about Frank's past. Along the way, they learn to rely on each other, confront their fears and insecurities, and rediscover their love and affection for each other.
When they finally arrive at the pageant, they realize that Olive is not the stereotypical beauty queen, but a charming and unconventional girl who embodies the spirit of Little Miss Sunshine. Despite the judge's disapproval and the audience's confusion, Olive performs her talent show by dancing to Rick James' "Super Freak". In the end, the family is united in their support for Olive, and they celebrate their triumph and their togetherness on the journey back home.