Set in the early 1950s, this evocative and eloquent romantic drama revolves around Eilis Lacey, a beautiful woman from Enniscorthy, County Wexford, a small town in southeast Ireland, where she lives with her mother and sister Rose. She is unable to find employment, other than working weekends at a shop run by the spiteful Miss Kelly, nicknamed 'Nettles Kelly', and is not interested in the local young men.
Her sister writes to an Irish priest (Father Flood) in Brooklyn who arranges for her to go to the US to find a better future. She leaves but suffers from seasickness on the voyage and ends up being locked out of the toilet by her cabin neighbours. The woman in the bunk below her, an experienced traveller, helps her, giving her advice and support.
Eilis lives at a Brooklyn boarding house where she dines each night with the landlady and her fellow residents, all young women. She has a job at a department store but is shy and quiet when interacting with customers, garnering some criticism from Miss Fortini, her supervisor. Her letters from her sister make her homesick. She is visited by Father Flood, and he tries to help by enrolling her in bookkeeping classes. At a dance she meets Tony Fiorello, who becomes her boyfriend. She begins to feel more comfortable in New York, and she and Tony become more and more involved romantically.
Father Flood informs Eilis that Rose has died suddenly of an undisclosed illness. After a trans-Atlantic phone call reveals her mother is struggling to cope, Eilis returns home for a visit. Tony insists that they must get married first without telling family or friends. In Ireland, everybody seems to be conspiring to keep Eilis from leaving. Her best friend is getting married a week after her scheduled return journey, and her mother has already accepted the invitation on her behalf.
She fills in part-time at her late sister's old bookkeeping job, which leads to the possibility of a full-time job. She goes on dates with an eligible and well-off bachelor. Eilis starts to feel that she now has a future in Ireland that did not exist when she left and stops opening the letters she receives from Tony.
Miss Kelly, her former employer, meets with Eilis and relates that she has learned of Eilis' marriage in New York. Agitated, Eilis is reminded of what life is like in such a small town. She informs her mother of her marriage and that she is leaving for Brooklyn the next day. On the crossing, she offers guidance to a young woman making her own first trip to Brooklyn. The film ends with Eilis and Tony reuniting and happily embracing.