Seward is the administrator of an insane asylum not far from Count Dracula's first English home, Carfax. Throughout the novel, Seward conducts ambitious interviews with one of his patients, R. M. Renfield, in order to understand better the nature of life-consuming psychosis, or as he calls it, zoophagous. As a psychiatrist, Seward enjoys using the most up-to-date equipment, including using a recording phonograph to record his interviews with his patients and his own notes. Several chapters of the novel consist of transcriptions of Seward's phonograph recordings. One of the main contributions made by Dr. Seward is his recordings of the events depicted from his personal perspective as a doctor; allowing the reader to gain a scientific understanding of the behavior of vampirism through his behavioral analysis of Renfield.
He is best friends with Quincey Morris and Arthur Holmwood. All three propose to Lucy Westenra on the same day. Although Lucy turns down Seward's marriage proposal, his love for her remains, and he dedicates himself to her care when she is suddenly taken ill.
He calls in his mentor, Abraham Van Helsing, to help him with her illness, and he helps Seward to realize that Lucy has been bitten by a vampire and is doomed to become one herself. After she is officially destroyed and her soul can go to heaven, Seward is determined to destroy Dracula. The novel's epilogue mentions that Seward is now happily married.
Seward often appears in different screen adaptations of Dracula but in a wide variety of different roles. He is often referred to as "Jack" Seward. The most common change is to portray him not as Lucy's suitor, but as Mina Harker's father (or sometimes Lucy's father). This was almost certainly based on the Hamilton Deane - John L. Balderston stage adaptation. Sometimes he is portrayed as just doctor with no familial or romantic connections to other characters.