Based on George M. Cohan's musical play, a stubborn Irishman resents his daughter's marriage and refuses to work or talk to his son-in-law until his granddaughter finally melts his heart.
In Ireland Timothy Fogarty (Arthur Shields) tells Michael Noonan (Charles Winninger) he is going to the USA. Nellie Noonan (Judy Garland) gives her father dinner. Jerry Kelly (George Murphy) wants to go to America and asks Nellie to marry. She agrees and sings "A Pretty Girl Milking a Cow." When Nellie tells her father, he gets upset. Nellie stops him from fighting Jerry. At a pub Noonan learns of their wedding and finds them at home. Noonan says he won't speak to Jerry but says Nellie must go with her husband, and he gives her sixty pounds dowry.
On the boat Jerry tells Nellie he wants to be a policeman. Noonan tells Timothy he plans only a short visit. Noonan refuses to get a job even when the Fogartys tell him of building work. Jerry studies to be a citizen. Jerry, Nellie, and Noonan are sworn in as citizens. Nellie is pregnant, and Jerry becomes a policeman. Nellie has a girl but dies as Jerry and Noonan cry. Jerry hires a woman to care for the baby; but Noonan argues with her and makes her leave. Jerry lets Noonan take care of the child.
Jerry is promoted to captain. Grown-up Nellie Kelly (Judy Garland) meets Dennis Fogarty (Douglas McPhail) in a parade and sings "It's a Great Day for the Irish." Noonan still won't shake hands with Jerry. Nellie sings "A Pretty Girl Milking a Cow" as Jerry remembers her mother. Dennis brings Nellie candy and asks her to a dance. She asks him to give her grandfather a job. Nellie takes Noonan to the Fogarty construction site. Noonan tells Dennis he is not in a union and complains of scabs, creating a disturbance. Nellie explains, and Noonan leaves. Jerry gives Nellie a new dress; but Noonan threatens to leave if she goes out. Nellie calls Dennis she can't go; but Timothy has Noonan arrested, so Nellie can go to the party at the Waldorf. A judge fines Noonan $25 for contempt of court. Dennis gets Nellie to sing, "Singing in the Rain." Noonan gets out of jail, because Timothy paid the fine. Noonan complains to Nellie and Dennis and wants to fight; but Jerry arrives to calm him down. Nellie asks Noonan why he hates Jerry, and Noonan leaves. At a police ball Dennis and others sing "Nellie Kelly I Love You." Nellie dances with her favorite, Jerry. Nellie and Dennis find her Noonan driving a carriage and are happy he got a job.
This celebration of the Irish immigrant experience contrasts
a Irishman with a temper who drinks and avoids work with a conscientious
policeman while the love of a woman keeps the family together.