On Christmas Day, Jim Dear gives his wife Darling a female American Cocker Spaniel as a gift. Darling names her Lady, and she fits right in. Lady grows and becomes friends with her neighbor dogs; the elder Bloodhound, Trusty, and the feisty Scottish Terrier, Jock. Meanwhile, a nameless Schnauzer-mutt, Tramp, spends his days wandering the streets of New Orleans in search of food and causing trouble for the dog catcher Elliot. After freeing his friends, Bull and Peg from Elliot's carriage, he runs away and ends up in the Dears' backyard. Lady, beside herself after being ignored by the adults, finds Tramp and tries to give away his position until he points out that Darling is having a baby. He warns her that her owners will start to ignore her, but she does not believe him. Jim and Darling have a girl, Lulu, who they devote their lives to.Jim and Darling take Lulu out and leave Darling's Aunt Sarah to house sit. As she goes upstairs to practice her singing, her two cats, Devon and Rex begin to create a mess with Lady caught in the middle. Believing Lady to be the cause of it all, Aunt Sarah takes Lady to the pet store and has a muzzle placed on her. Lady escapes, but is threatened in an alley by a dog, Isaac. Luckily, Tramp saves her and helps remove her muzzle with a statue before taking the "scenic route" back to Ladies house, in order to avoid Elliot, as Lady lost her collar. They grow close and eat at a restaurant. Afterwards, Tramp reveals that he once had owners, but was abandoned once they had a child. They are found by Elliot and chased, resulting in Lady being captured. Tramp hesitates before escaping. Lady meets the other pound dogs who talk about Tramp and his exploits. The next morning, Jim and Darling pick up Lady and kick Aunt Sarah out. Lady begins to bond with Lulu.Tramp discovers that Peg and Bull have been adopted, causing him to regret leaving Lady behind. He goes to her house to apologize, which she appreciates, but does not want to see him. However, a rat plaguing the house, sneaks into Lulu's room. Lady is put away, as Elliot arrives to interview Jim and Darling. Lady manages to call Tramp who sneaks into the house and kills the rat, but is caught by Jim. As Elliot takes Tramp away to be euthanized, Lady uncovers the rat and proceeds to chase down the carriage with Trusty and Jock's help. The dogs overturn the carriage, rescuing Tramp. The Dears arrive and decide to adopt Tramp. By Christmas, Tramp has been fully accepted into the Dear household while Jock's owner has adopted two young puppies, Dodge and Ollie. Lady and Tramp happily spend the holidays with their family.