Clarissa is a middle-aged, upper-middle-class woman living in post-WWI London. As she runs errands and prepares to host a high-society event, she reflects deeply on her past, particularly her youth at her family's country home, Bourton. She projects a perfect societal exterior but experiences a rich internal life regarding her past choices in love and marriage.

Peter is an old friend and former suitor of Clarissa who has recently returned to London from India. He is highly emotional and prone to playing with a pocketknife when anxious. He tries to reconcile his current engagement to a younger woman in India with his lingering feelings for Clarissa.

In her youth, Sally was a vivacious and daring figure who deeply infatuated Clarissa. She represents the uninhibited freedom of the past, standing apart from the conservative London society the Dalloways currently inhabit. She later settles into a traditional domestic life with a husband and five sons.

Richard is a steady politician working for the British government. He provides Clarissa with stability and space, differing from the emotionally demanding Peter Walsh. Though he cares deeply for his wife, he finds it difficult to verbalize his feelings, relying instead on gestures like buying flowers.

Septimus is a working-class veteran of World War I who suffers from severe shell-shock. Before the war, he was an idealistic young man who loved literature, but the trauma of combat has left him emotionally numb and prone to vivid hallucinations. He views the world with suspicion and struggles to communicate his internal terror.

Seventeen-year-old Elizabeth is the only child of Clarissa and Richard. She possesses a quiet nature and a striking appearance that draws attention. Uninterested in the socialite path her mother walks, she prefers the company of her dog and her history teacher.

Rezia is a young Italian woman who left her home in Milan to marry Septimus. In London, she feels isolated and overwhelmed by her husband's deteriorating mental state. She works as a hat-maker and attempts to follow the doctors' advice to engage Septimus in the real world.

Hugh is an old childhood friend of Clarissa's who maintains a polished and slightly pompous presence in London society. He is wealthy, acutely aware of social standing, and holds a minor position at Court. Peter Walsh and Richard Dalloway both find him somewhat intolerable.

Miss Kilman is Elizabeth's history teacher and companion. An unmarried, working-class woman of German descent, she turns to religious extremism to cope with her feelings of poverty and marginalization. She harbors a bitter resentment toward wealthy women like Clarissa.

Lady Bruton is an imposing aristocratic woman with a strong interest in politics and emigration to Canada. She commands respect in her social circles and prefers the company of men over women, often calling upon friends like Richard and Hugh to help her draft letters to the newspaper.

Sir William Bradshaw is a prominent, wealthy psychiatrist who treats mental illness through a philosophy he calls proportion. He is commanding, clinically detached, and fundamentally unable to empathize with the true depths of his patients' suffering.

Dr. Holmes is a general practitioner who represents the stiff upper lip mentality of British society. He insists that there is nothing truly wrong with Septimus, advising him to simply take an interest in outside things.

Evans was Septimus's officer and close friend during World War I. He was killed just before the armistice. He does not exist in the present timeline but remains a powerful presence in Septimus's mind.

Daisy is a young married woman living in India. She represents Peter's desire for youth and a fresh start, though he feels insecure about their relationship due to the calculated letters she sends him.

Evelyn is Hugh Whitbread's wife. She frequently suffers from obscure internal ailments that require trips to London doctors, prompting her husband's interactions with Clarissa and Richard.

Miss Isabel Pole was a teacher who inspired a younger Septimus before the war. He wrote poetry for her, which she corrected in red ink.

Lucy is the housekeeper at the Dalloway residence. She diligently handles the practical preparations for Clarissa's evening event, cleaning the house and offering to mend her employer's dress.