The play is set in the 1600's in Europe during the Thirty Years' War. The Recruiting Officer and Sergeant are introduced, both complaining about the difficulty of recruiting soldiers to the war. A canteen woman named Mother Courage enters pulling a cart that she uses to trade with soldiers and make profits from the war. She has three children, Eilif, Kattrin, and Swiss Cheese. The sergeant negotiates a deal with Mother Courage while Eilif is led off by the recruiting officer. One of her children is now gone.
Two years from then, Mother Courage argues with a General's cook over a capon, or chicken. At the same time, Eilif is congratulated by the General for killing peasants and slaughtering their cattle. Eilif and his mother sing "The Song of the Girl and the Soldier." Mother Courage scolds her son for the killings and boxes him on the ear.
Three years later, Swiss Cheese works as the paymaster. The camp prostitute, Yvette Pottier sings "The Fraternization Song." Mother Courage uses this song to warn Kattrin about involving herself with soldiers. Before the Catholic troops arrive, the Cook and Chaplain bring a message from Eilif. Swiss Cheese hides the regiment's paybox. Swiss Cheese is captured while attempting to return the paybox to the General. Mother Courage sells her cart and uses the money to try and barter with the soldiers to free her son. Swiss Cheese is shot anyway. Mother Courage does not acknowledge the body and it is thrown into a pit.
Later, Mother Courage waits outside of the General's tent and sings the "Song of Great Capitulation" to a young soldier waiting for the General as well. The song offends the soldier and Mother Courage decides she does not want to complain.
When the General's funeral approaches, Mother Courage discusses with the Chaplain about whether the war will continue. The Chaplain then suggests to Mother Courage that she marry him, but she rejects his proposal. Mother Courage curses the war because she finds Kattrin disfigured after collecting more merchandise.
Two peasants wake Mother Courage up and try to sell her merchandise while they find out that peace has broken out. The Cook appears and creates an argument between Mother Courage and the Chaplain. Mother Courage parts from the town while Eilif enters, dragged in by soldiers. Eilif is executed for killing peasants but his mother never finds out. When the war begins again, the Cook and Mother Courage start their own business.
The seventeenth year of the war marks a point where there is no food and no supplies. The Cook wants to open an inn in Utrecht with Mother Courage, but he refuses to harbor Kattrin. Mother Courage will not leave her daughter and they part separate ways with the Cook. Mother Courage and Kattrin pull the wagon by themselves.
The Catholic army attacks the small Protestant town of Halle while Mother Courage is away from town, trading. Kattrin is woken up by a search party that is taking peasants as guides. Kattrin fetches a drum from the cart, climbs onto the roof, and beats it in an attempt to awake the townspeople. Though the soldiers shoot Kattrin, she succeeds in waking up the town.
Early in the morning, Mother Courage sings to her daughter's corpse, has the peasants bury her and hitches herself to the cart. The cart rolls lighter now because there are no more children and very little merchandise left.
