An Irish immigrant working for Edgar’s neighbor and a sleepwalker himself, who narrates a story within the story. He becomes a central figure in Edgar's investigation due to his mysterious past.

Referred to as Sarsefield, this character is a surgeon and former tutor of Edgar who provides a stabilizing influence. He returns to America after Edgar’s disappearance and becomes involved in recovering important documents.

Edgar’s uncle’s closest neighbor and employer of Clithero, who assists Edgar and Sarsefield throughout the story. He provides support to Edgar’s family and guidance in their time of need.

An antagonist in Clithero's narrative, regarded as dissolute and disruptive. His relationship with his twin sister Euphemia plays a significant role in the conflict of Clithero's past.

Arthur Wiatte’s twin sister and Sarsefield’s love interest, who financially supports those around her. Her life intertwines with key events in the narrative of Clithero and has a lasting impact.

Raised by Euphemia and beloved by Clithero, she is mistakenly endangered due to her uncle's malice. Her resemblance to Euphemia confounds Clithero’s recollection and judgment.

Fiancée to Edgar and the recipient of his narrative letter, absent from the direct storyline but integral as the audience of Edgar's writings. She represents a distant yet influencing presence.

Mary's brother whose earlier death sets off the chain of investigations led by Edgar. Known for his early philosophical views, his past and possessions become central to Edgar’s inquiries.

A merchant claiming rights to the money entrusted to Waldegrave, which complicates Edgar's engagement plans. His fleeting involvement influences Edgar’s sleepwalking episodes.

Edgar’s uncle and father figure who takes him in after the death of Edgar’s parents. Known for his past military career and roles of guidance and protection in Edgar’s life.

A Native American woman referred to by Edgar with a nickname derived from literature. Her residence becomes a scene of conflict and holds symbolic importance.

A collection of mostly unnamed Pennsylvania settlers and Native Americans who exist on the periphery of the story. Their interactions with Edgar provide a broader social context to the narrative.