Krapp is a disheveled, 69-year-old man who spends his birthday alone listening to audio recordings he made decades earlier. He struggles with physical ailments, including chronic constipation, and a long-standing addiction to alcohol and bananas. A failed writer who isolated himself for the sake of his work, he now wrestles with regret and the conflicting feelings of his past selves recorded at ages thirty-nine and in his twenties.

Bianca is a woman Krapp lived with on and off during his twenties. The thirty-nine-year-old version of Krapp expresses relief that their relationship ended, though he still fondly recalls her warm eyes long after their separation.

Krapp's mother is an ailing woman whose death is a focal point of Krapp's thirty-nine-year-old recording. Krapp recalls sitting on a bench near her window, waiting for her to pass away so he can be free of the burden of her decline.

Krapp's father is a figure from Krapp's early life whose passing is noted on the earliest recording. His death coincides with the young Krapp outlining resolutions to drink less and pursue a less consuming sexual life.

This unnamed woman shares an intimate afternoon stroll and a quiet moment in a punt boat with the thirty-nine-year-old Krapp. Krapp eventually ends the relationship to focus on his intellectual work, a decision that haunts him in his old age as he repeatedly rewinds the tape to listen to the memory of lying across her.

Fanny is an older prostitute who visits the sixty-nine-year-old Krapp twice in the past year. Krapp notes her surprise at his enduring physical capabilities despite his advanced age.

The nurse is a dark-haired young woman in a white, starched uniform whom Krapp notices while waiting outside his mother's window. She strongly rejects Krapp's attempts to speak to her, creating a memorable moment of rejection in his past.

A small white dog that Krapp plays with while waiting outside during his mother's final moments. Krapp throws a black ball for the dog and later regrets letting the animal keep the toy.