The novel opens in el Rancho de las Rosas in Aguascalientes, Mexico. 12-year-old Esperanza lives a charmed life with her Papa, Mama, Abuelita, and several servants and workers. Esperanza is very close to Papa. He feels a strong connection to the land and teaches Esperanza how to listen to the heartbeat of the earth. The day before Esperanza's thirteenth birthday, she pricks her finger on a thorn - a sign of bad luck. Later that night, Esperanza and her family receive the terrible news that Papa has been killed by bandits.
Papa's stepbrothers, Tío Luis and Tío Marco, are both powerful men in Aguascalientes. Together, they try to manipulate the situation after Papa's death in order to seize el Rancho de las Rosas. Tío Luis offers to marry Mama and threatens her when she turns him down. Shortly after Papa's death, Esperanza wakes up to find their home on fire. Everybody escapes, but Abuelita hurts her ankle and all of the crops are burnt to a crisp. Without a home or any source of income, Mama agrees to marry Tío Luis. Later, she tells Esperanza that her acceptance is simply a diversion so she can plan their escape to the United States. One night, Alfonso, Hortensia, and Miguel sneak out of Aguascalientes and leave Mexico for good. Abuelita must stay behind in a convent because her injury prevents her from traveling.
Newly penniless, Esperanza struggles to adjust to her new social status during the journey to the United States. After several days on the train, the group arrives in California. Alfonso's brother, Juan, comes to pick them up. Juan and his wife, Josefina, have three children: Isabel, who is a bit younger than Esperanza, and twin babies, Pepe and Lupe. Esperanza is shocked to see her new home: a cramped, shared cabin in a migrant workers' camp.
Isabel teaches Esperanza how to do household chores. Once Isabel goes to school, Esperanza must care for the babies and the house on her own while everyone else works in the fields. She has never done manual labor before and struggles to learn. She develops a rivalry with Marta, a young politically-minded woman who is organizing the migrant workers to strike for better living conditions.
One day, a dust storm ravages the San Joaquin Valley. Everyone returns home safely, but Mama becomes sick with Valley Fever. Unwell and unable to work, Mama stays at home while Esperanza starts working in the field. Mama becomes sicker and must be moved to the hospital. In order to pay the medical bills, Esperanza takes on more work, despite the danger that the upcoming strike may pose.
The strike occurs during the asparagus harvest. However, immigration officials break it up and haul several strikers away to be deported. Esperanza later finds Marta hiding in a shed. Instead of turning her in to the officials, Esperanza helps Marta escape. In her new role as head of the house, Esperanza grows tremendously and is able to balance all of her chores while looking after Isabel and the babies.
Eventually, Mama returns from the hospital. Esperanza's contentment is short-lived, though, when Miguel loses his mechanic job to workers from Oklahoma who are willing to work for less. Esperanza becomes outraged and picks a fight with Miguel about the social position of Mexican migrant workers in the United States. Miguel is gone the next morning. Soon after his departure, Esperanza discovers that the money she had been saving to bring Abuelita to the United States is gone. Frustrated and angry, Esperanza throws herself into her work.
A few days later, Miguel returns to California with Abuelita, whom he managed to sneak out from under the watchful eye of Tío Luis. It turns out he took Esperanza's money to do exactly what she had planned to do with it. In the year after Papa's death, Esperanza's life comes full circle. Her family is together and she has found happiness once again.