The antics of tomboyish Maria, a novice at the abbey in Salzburg, concern the Mother Abbess, who is unsure whether Maria wants to become a nun.  To allow the girl to test her feelings, the Mother Abbess sends Maria to be the governess for the seven children of the widowed Baron Georg von Trapp, a retired naval officer.

The children are at first hostile to Maria, but she soon wins them over.  The Baron, a strict disciplinarian, leaves to visit Baroness Schraeder and, while he is gone, Maria allows the children greater freedom and teaches them to sing.

The children become so excited when the baron returns that they fall out of a rowboat in the lake.  The accident precipitates an argument between Maria and the baron, and he orders her to leave; but when he goes into the house and finds the children entertaining his friend Max and the Baroness with a song, he asks Maria to stay.  Max later suggests that they enter the Salzburg Festival as a singing group, but the Baron refuses.

Maria becomes aware that she is falling in love with the Baron and returns to the abbey.  The children follow her there and try to persuade her to return; when the Mother Abbess learns of their visit, she sends Maria back to the Trapp home.  Maria again decides to leave when she hears that the Baron plans to marry the Baroness, but the Baroness realizes that he loves Maria and releases him.  He then marries Maria, and while they are away on their honeymoon, the Nazis take over Austria.

Max, taking advantage of the Baron's absence, enters the children in the Salzburg Festival.  When Maria and the Baron return, he forbids the children to appear at the festival.  The Baron learns that the Nazis, to whom he is violently opposed, have ordered him to take command of a ship.  The Trapps plan an escape but are stopped by Storm Troopers.  Max convinces them that they are on their way to the festival and that the Baron is leaving for his ship immediately after the performance.  The Trapps win first place and, using their exit song to escape, they take refuge in the abbey.  The Nazis learn their whereabouts and surround the building, but the family escapes through a secret tunnel to the nearby mountains.