Oedipa is a suburban California housewife who finds herself appointed as the executor of her wealthy ex-boyfriend's estate. Initially living a conventional, disconnected life with her husband, she travels to San Narciso to sort out the complicated will. Her investigation leads her into a bizarre, confusing world of signs, symbols, and alternative postal networks. She actively searches for meaning and order in a chaotic, postmodern society.

Pierce is a deceased, immensely wealthy California real estate mogul whose sprawling assets form the basis of the story's central mystery. Though he never physically appears, his influence touches nearly every aspect of the society Oedipa investigates, from stamp collections to defense contractors. He possessed a habit of adopting different voices and stereotypical accents for his own amusement.

Metzger is a handsome lawyer assigned to help Oedipa unravel the details of Pierce Inverarity's vast estate. He is a former child actor who starred in films under the stage name Baby Igor, a past he readily shares while drinking wine and tequila. He accompanies Oedipa on her initial investigations around San Narciso, blending professional duties with casual seduction.

Dr. Hilarius is Oedipa's eccentric psychiatrist who operates a practice treating suburban housewives. He frequently contacts Oedipa to recruit her for his ongoing studies testing the effects of LSD and other hallucinogens. He exhibits highly erratic behavior and vocalizes strange, paranoid theories regarding his own past and the people around him.

Mucho is Oedipa's husband, currently working as a radio disc jockey after an unfulfilling career as a used car salesman. He suffers from a crisis of confidence and deep dissatisfaction with the world, finding modern life isolating. He communicates with his wife primarily through sparse, empty letters once she leaves for San Narciso.

Mike is a fervent right-wing conspiracist and a member of the Peter Pinguid Society. He vehemently opposes the government's monopoly on mail delivery and utilizes alternative, private networks to send messages. He is writing a history of the United States Postal Service and introduces Oedipa to the concept of underground communication channels.

Genghis Cohen is a highly skilled stamp expert hired to analyze the philatelic assets within the Inverarity estate. He meticulously reviews the collection and points out strange irregularities, such as unexpected watermarks shaped like post horns. His historical knowledge helps Oedipa contextualize the symbols she encounters during her investigation.

Stanley is an employee at the Yoyodyne Corporation who is frustrated by the restrictive patent laws of the United States. He absentmindedly sketches a muted post horn symbol while working, which catches Oedipa's attention. He possesses specialized knowledge about fringe scientific theories and underground inventors.

John is a Berkeley-based scientist attempting to build a perpetual-motion device based on the theoretical Maxwell's Demon. He requires specially designated "sensitives" to operate his machine through pure mental effort. He views the laws of thermodynamics with a mix of academic rigor and mystical belief.

Randolph is a theater director who stages a chaotic Jacobean revenge play in San Narciso. When Oedipa approaches him to ask about specific lines and historical references in his production, he dismisses her inquiries. He insists that the play is purely entertainment and warns her against overanalyzing minor details.

Emory is an English professor and an expert on Jacobean revenge plays. He authored the foreword to the specific anthology that Oedipa uses for her research. He provides extensive historical context about European postal monopolies, religious propaganda, and theater history.

Mr. Thoth is an elderly resident of a care home who spends his days recounting vivid dreams and memories of his grandfather. His stories involve his grandfather's violent experiences riding for the Pony Express and encountering mysterious adversaries. He shows Oedipa a historical ring bearing the image of a post horn.

Miles is a hotel employee and a member of the local rock band, the Paranoids. He exhibits a highly suspicious demeanor, immediately assuming Oedipa has ulterior motives when she offers to pass along his band's demo tape. He frequently travels with his bandmates and a group of teenage fans.

Roseman is Oedipa's local lawyer who struggles to maintain a professional boundary with his clients. Rather than offering concrete legal advice regarding her sudden appointment as an executor, he impulsively suggests that Oedipa run away with him.

Manny is a lawyer representing a client who is suing the Inverarity estate over an unpaid debt for a bizarre delivery of human bones. He hides out near a lake to avoid dangerous clients, pulling Metzger and Oedipa into a convoluted story about wartime scavengers and cigarette filters.