During a one-night shore leave in New York City, ship stoker Bill Roberts (George Bancroft) saves young prostitute Mae (Betty Compson) from a suicide attempt. He steals some clothes for her and invites her to the Sandbar saloon to have some fun. In a fit of drunken bravado he summons a minister and marries her.
In the morning he dismisses the marriage as a joke and goes off to sea. However, as the ship departs, he realizes what he has done, changes his mind, jumps into the sea and swims back to the shore. He finds Mae at the court, being tried for stealing the clothes. He storms inside, saying he's her husband, and confesses, so the judge sentences him to 60 days in jail. He tells his wife this isn't a long "cruise", and it's going to be his last if she waits for him. She promises to wait forever.
In 1999, the film was selected for preservation in the National Film Registry.
The Docks of New York provides examples of the following tropes:
- Bar Brawl: Subverted. There are several minor fights in the Sandbar, but every time they are quenched before things become too ugly.
- Bathroom Stall Graffiti: On the walls of the ship's engine room.
- Beta Couple: Andy, Third Engineer on Bill's ship, and his wife Lou (played by Olga Baclanova). While the story's main focus is the marriage of Mae and Bill, we also witness the conclusion of their less than happy marriage, ending with Lou shooting Andy during his attempt to rape Mae, and surrendering to police.
- Big Damn Kiss: Notably averted. The movie freely depicts sexuality, but the couple shares surprisingly little intimacy on screen. See also Happily Ever After.
- City of Adventure: Described in the Opening NarrationThe waterfront of New York — the end of many journeys, the beginning of many adventures. Miles of docks wait day and night for strange cargo — and stranger men.
- The Cynic: More or less everyone, but especially Andy, as lampshaded by one of the stockers: "He's the most even-tempered guy I ever knew — always sore!".
- Death by Woman Scorned: Lou kills Andy.
- Dysfunction Junction: Made especially clear during Bill and Mae's dialogue at the bar, when they both reveal they have never been married because nobody would marry such a person.
- Driven to Suicide: After Bill leaves Mae we see her overlaid with a transparent image of waves - she's clearly thinking of a new suicide attempt.
- Embarrassing Tattoo: Bill's arms are covered with tattoos depicting naked women and female names.
- Escalating Brawl: Averted several times in the Sandbar.
- Fetch Quest: After saving Mae, Bill leaves her with Lou. She promptly kicks him out of the room, first sending him to bring Mae a hot drink (from the bar where he's not welcome), then to find her new clothes (which he eventually steals, breaking into a closed shop). Both quests are shown in detail, perfectly characterising Bill as a tough and reckless, but not overly violent man.
- Hard-Work Montage: An Ur-Example: the film begins with a montage showing stokers working hard in the hellish engine room.
- Hate Sink: Andy. He's not an antagonist, creating no obstacles for the main characters, but he's a major Jerkass who has ruined Lou's life, picks on Bill and later attempts to rape Mae.
- Hope Spot: Mae believes Bill, telling him she would be a good wife. The worse she feels in the morning, realizing that he never intended to stay with her.
- Interrupted Suicide: Bill saves Mae from drowning, and that's how they meet.
- Introduction by Hookup: This is what happens from Bill's point of view. Mae takes their meeting seriously.
- Jerk with a Heart of Gold: Bill, eventually.
- The Masochism Tango: Lou and Andy.
- No Antagonist: Nobody is opposing the main characters; the main conflict develops within Bill.
- Nostalgia Filter: Played straight in the opening scenes, first praising coal engines ("These were the days before oil fuel made stocking a lady's job — when stokers earned their pay in sweat and coal-dust") and than regretting the Sandbar saloon ("vanished now — wiped out by commerce and reform. But that night it was wide awake and roaring"). Deconstructed later, when we see what a hellhole the Sandbar is.
- Not-So-Safe Harbor: The titular docks of New York.
- The Piano Player: Not present as a human character, but there are several close-ups of a playing autopiano at the Sandbar bar.
- Sinister Minister: Subverted. "Hymn Book" Harry, who is invited to marry Mae and Bill, is introduced as a dark and creepy figure, but turns out to be a Good Shepherd, disgusted by this travesty of a marriage, but reluctantly performing it.
- What Did I Do Last Night?: Discussed and subverted during Andy and Bill's dialogue over breakfast. Andy suggests that Bill doesn't remember he got married last night. Bill remembers everything; he just doesn't take it seriously.
- "What Now?" Ending: After Bill returns to Mae, they have a brief dialogue, after which he is taken away, and she stays in the courtroom, with camera tracking away until she disappears from view. That's it. The movie leaves it to the audience to decide whether there's going to be a Happy Ending after all.
- Wretched Hive: The docks, particularly the Sandbar saloon.
- Your Cheating Heart: Both Andy and Lou. He comes to the Sandbar looking for a hook-up, and finds her dancing and kissing with a stranger. Awkwardness ensues.