When Lady's owners start acting cold towards her, she meets Tramp who overhears her telling the problem to her two best friends Jock and Trusty. He explains they are having a baby in a negative light. Immediately, Jock and Trusty begin to dislike him.

Shortly after Lady's owner's have the child, they go on a holiday. Lady is left with Aunt Sarah and her two cats. After a dispute with the cats and a misunderstanding, Lady gets a muzzle. Tramp helps remove the muzzle and the two spend a night together including a romantic dinner. Lady falls in love with Tramp.

While Lady is being escorted home by Tramp she is caught by the dog-catcher. When she is at the pound, she discovers that Tramp has had many lovers before Lady.

When Lady is claimed by Aunt Sarah she confronts Tramp about his lovers, and tells him she won't ever talk to him again. Moments later, she sees a rat heading for the baby's room. Tramp helps her kill it but during the scuffle, the cot is knocked over. Aunt Sarah assumes Tramp intended to do harm and calls the dog-catchers.

Jim Dear and Darling arrive as the dog-catcher leaves. They release Lady who was locked in the basement. Lady leads them to the dead rat which proves Tramp's innocence. Jock and Trusty overhear and chase after the dog-catchers wagon. They bark at the horses, and the wagon topples. Jim Dear and Lady arrive by car, and Lady is delighted to be re-united with Tramp. Unfortunately, Trusty's leg is injured.

That Christmas Tramp becomes part of their family and gets his own collar and license. Lady and Tramp have a litter of four puppies, and Jock and Trusty come to visit.