In the first part of the novel, Mohun Biswas is an Indo-Trinidadian who begins his life inauspiciously when he is born under several unfavorable conditions. A Hindu pundit is called in to name him and cast his horoscope; he predicts that this will be a child who brings bad luck to his family. The prophecy seems to begin to fulfill itself when, as a child, Mr. Biswas is indirectly and unintentionally responsible for the death of his father, and his family is eventually broken apart as a result. As the youngest child, he stays with his mother, but she lacks the capacity to nurture him and influence his upbringing. He basically becomes a child of circumstance, and his life becomes more or less accidental. In his job as a sign painter for the Tulsi store, he is attracted to a young girl’s smile. It inspires him to write her a note which her family interprets as a love letter, and he suddenly finds himself engaged, with no way of extricating himself from the situation.

As a married man, Mr. Biswas and his wife Shama live in Hanuman House with Shama’s mother and multitudes of her relatives. He becomes a buffoon, a clown, a rebel, and is constantly in conflict with one member of the family or another. Eventually his offense is so great that he is sent from the house to run a store on one of the Tulsi properties. The endeavor is successful until Shama wants to have the house blessed; after that, Mr. Biswas experiences financial difficulties and makes ill-advised decisions that result in getting him deeper into debt. Seth, Mrs. Tulsi’s brother-in-law and manager of Tulsi affairs, offers him a position as a driver on one of the Tulsi sugar estates, and he accepts, under Shama’s coaxing.

On the sugar estate, the family lives in a barracks shared with eleven other families. Mr. Biswas is impatient to build a house, but he does not have very much money. The house is built bit by bit, and the promise of a nice house diminishes as economic considerations necessitate the substitution of substandard supplies for quality materials. Between his house, his growing family, and his job, Mr. Biswas begins to have worries, the worries become anxieties, and the anxieties become full-blown fears. One night during a storm, his house is almost blown away and he breaks down completely. He is taken back to Hanuman House, where Shama is about to give birth to their fourth child, and he recuperates in the solid security and comfort of the house he has professed to hate. When it is time for him to make a decision, he decides to leave Hanuman House and his family behind and make another attempt at setting out on a new life.

In the second part of the novel, Mr. Biswas goes to Port of Spain and finally begins to establish himself as an individual, settling into a satisfying, although low paying, job as a journalist. He reconciles with his family, and Mrs. Tulsi invites them to live in her house in Port of Spain. They enjoy their time there, and Mr. Biswas feels that he is becoming more detached from the hold of the Tulsis. Nonetheless, Mrs. Tulsi continues to use her manipulative powers on Mr. Biswas, and he eventually finds himself a reluctant resident of the Tulsi estate in Shorthills.

Seth has had a falling out with the Tulsis, and life is very difficult as the house deteriorates from neglect and abuse. The children especially face unpleasant challenges, and Mr. Biswas builds another house for his family. This house is also doomed, and more bad judgment on Mr. Biswas’s part causes a fire that barely avoids destroying the house. The family does not have to stay in the house long, however, since Mrs. Tulsi’s house in Port of Spain becomes vacant again, and Mr. Biswas moves back, occupying two rooms, and sharing the rest of the house with other members of the Tulsi family. Conditions at the house get out of control as more and more people move into the house and it becomes a den of noise and uncleanliness.

As Mr. Biswas’s son Anand starts college, Mr. Biswas begins to sink again into despair. He is pulled out of it when he is offered a new job as a community Welfare Officer with better pay. The job eventually also provides him with a car, and Mr. Biswas achieves new status in the house. The status turns out to be temporary, as his family is obliged to move to a tenement in order to make improvements to the house in anticipation of the return of Owad, Mrs. Tulsi’s son who has been studying medicine in England. The family is allowed to move back into the house after three months, but their stay is brief because of conflict between Owad and Anand, then Owad and Mr. Biswas, and finally Mr. Biswas and Mrs. Tulsi.

As Mr. Biswas looks for a place to live, he is not holding out much hope, but he is approached by a man who wants to sell his house, and circumstances arrange themselves so that Mr. Biswas agrees to make the purchase. Unfortunately, this turns out to be another incident of bad judgment, as the house has more problems than he realized, and the family is once again disheartened. They work to get the house livable and are able to enjoy some time in it, making it their own, before Mr. Biswas loses his job because the Community Welfare Department is abolished.

He goes back to his job at The Sentinel, and now his money worries are magnified since he has acquired a great deal more debt but lost a great deal of his income. He eventually has a series of heart attacks and ultimately dies, but he leaves behind a house that will shelter his family for as long as they live.