Semyour S. Kety was born in Philadelphia, Pennsylvania in 1915. Raised in a humble family household in Philadelphia, Kety was intellectually challenged and stimulated. As a child, Kety was involved in a car accident that injured his foot. Though he could still walk, Kety remained slightly physically impaired.

For his education, Kety stayed in his home town of Philadelphia. Kety attended Central High School in Philadelphia and found himself excelling greatly in chemistry. Running his own experiments in his homemade laboratory, Kety found a passion for chemistry. Throughout high school, he pursued his interest in the physical sciences and also gained knowledge of both Greek and Latin. Kety attended college and medical school at the University of Pennsylvania, from which he graduated in 1940. He did a rotating internship at the Philadelphia General Hospital, but that was the extent of his clinical training. After finishing his internship, Kety went into research.

Following his internship, Kety decided to continue his research of lead poisoning. The National Research Council post-doctorate fellowship, received by Kety to continue his research, began in 1942. Kety worked under the supervision of lead poisoning specialist Joseph Charles Aub. Only after Seymour arrived prepared to start his fellowship did he learn that Aub changed his area of study — he was now working with traumatic and hemorrhagic shock. Joseph Aub changed his work to study the shock because it was a time of war, and the research was pressing. While working with Aub, Kety found the circulation of the heart to be fascinating. Instead of returning to Harvard, Kety went to his alma mater, the University of Pennsylvania. While back in Pennsylvania, Seymour worked with Carl Schmidt, an expert in cerebral circulation. Kety became a pharmacology instructor at the university.

After collaborating with many doctors on various projects, Seymour S. Kety became the chairman of the department of psychiatry at Johns Hopkins University in 1961. After only one year, Kety resigned due to his lack of experience in psychiatry. He returned to his job as the Chief of Laboratory Science. Seymour, however, continued the research he was working on. He was researching the causes of schizophrenia. His focus was based on the genetic influences that cause the disease.

In 1981, Kety became a founding member of the World Cultural Council.

He never trained in psychiatry although he changed its course. In 1988 Kety and Louis Sokoloff were jointly awarded the NAS Award in the Neurosciences from the National Academy of Sciences. Kety also received awards from some of the most prestigious scientific groups, including the American Society of Arts and Sciences and the American Philosophical Association.