Upon her second husband's death, domineering matriarch Bernarda Alba imposes a 7-year mourning period on her household in accordance with her family tradition. Bernarda has 5 daughters, aged between 20 and 39, whom she has controlled inexorably and prohibited from any form of relationship. The mourning period further isolates them and tension mounts within the household.
After a mourning ritual at the family home, eldest daughter Angustias enters, having been absent while the guests were there. Bernarda fumes, assuming she had been listening to the men's conversation on the patio. Angustias inherited a large sum of money from her father, Bernarda's first husband, but Bernarda's second husband has left only small sums to his 4 daughters. Angustias' wealth attracts a young, attractive suitor from the village, Pepe el Romano. Her sisters are jealous, believing that it's unfair that plain, sickly Angustias should receive both the majority of the inheritance and the freedom to marry and escape their suffocating home environment.
Youngest sister Adela, stricken with sudden spirit and jubilation after her father's funeral, defies her mother's orders and dons a green dress instead of remaining in mourning black. Her brief taste of youthful joy suddenly shatters when she discovers that Angustias will be marrying Pepe. Poncia, Bernarda's maid, advises Adela to bide her time: Angustias will probably die delivering her first child. Distressed, Adela threatens to run into the streets in her green dress, but her sisters manage to stop her. Suddenly they see Pepe coming down the street. She stays behind while her sisters rush to get a look, until a maid hints that she could get a better look from her bedroom window.
As Poncia and Bernarda discuss the daughters' inheritances upstairs, Bernarda sees Adela wearing makeup. Appalled that Adela would defy her orders to remain in a state of mourning, Bernarda violently scrubs the makeup off her face. The other daughters enter, followed by Bernarda's elderly mother, Maria Josefa, who is usually locked away in her room. Maria Josefa announces that she wants to get married; she also warns Bernarda that she'll turn her daughters' hearts to dust if they cannot be free. Bernarda forces her back into her room.
It turns out that Adela and Pepe are having a secret affair. Adela becomes increasingly volatile, defying her mother and quarreling with her sisters, particularly Martirio, who reveals her own feelings for Pepe. Adela shows the most horror when the family hears the latest gossip about how the townspeople recently dealt with a young woman who shamelessly delivered and killed an illegitimate baby.
Tension explodes as family members confront one another and Bernarda pursues Pepe with a gun. A gunshot is heard outside. Martirio and Bernarda return and imply that Pepe has been killed. Adela flees into another room. With Adela out of earshot, Martirio tells everyone else that Pepe actually fled on his pony. Bernarda remarks that as a woman she can't be blamed for poor aim. Immediately she calls for Adela, who has locked herself into a room. When Adela doesn't respond, Bernarda and Poncia force the door open. Soon Poncia's shriek is heard. She returns with her hands clasped around her neck and warns the family not to enter the room. Adela, not knowing that Pepe survived, has hanged herself.
The closing lines of the play show Bernarda characteristically preoccupied with the family's reputation. She insists that Adela has died a virgin and demands that this be made known to the whole town. (The play alludes that Adela and Pepe had an affair; Bernarda's moral code and pride keep this from registering). No one is to cry.