George Snell was born in Bradford, Massachusetts, the youngest of three children. His father (who was born in Minnesota), worked as a secretary for the local YMCA; he invented a device for winding induction coils for motorboat engines. Snell was educated in the Brookline, Massachusetts schools and then enrolled at Dartmouth College in Hanover, New Hampshire where he continued his passion for mathematics and science, focusing on genetics. He received his Bachelor's degree from Dartmouth in 1926.

This experience "served to convince me that research was my real love," Snell wrote in his autobiography.[2]"If it were to be research, mouse genetics was the clear choice and the Jackson Laboratory, founded in 1929 by Dr. Clarence Cook Little, one of Castle's earlier students, almost the inevitable selection as a place to work." The Jackson Laboratory was (and still is) the world's mecca for mouse genetics.

Upon receiving the Ph.D from Harvard, George Snell was employed as a Teacher at Brown University, from 1930~1931.

After brief stints as teachers, in 1935 Snell joined the staff of The Jackson Laboratory in Bar Harbor on beautiful Mount Desert Island by the coast of Maine and he remained there for the entire balance of his long career. In Bar Harbor, he met and married Rhoda Carson. Together they had three sons, Thomas, Roy, and Peter. In his leisure time, Snell enjoyed skiing, a passion he developed during his years at Dartmouth, as well as tennis.

Snell received the Cancer Research Institute william B. Coley Award in 1978 for distinguished research in immunology. In 1988, he authored a substantial book, Search for a Rational Ethic, on the nature of ethics and the rules by which we live. It includes an evolution-based ethic founded on biological realities that he believed to be applicable to all human beings.

George Snell shared the 1980 Nobel Prize in Physiology or Medicine with Baruj Benacerraf and Jean Dausset for their discoveries concerning "genetically determined structures on the cell surface that regulate immunological reactions". Snell specifically "discovered the genetic factors that determine the possibilities of transplanting tissue from one individual to another. It was Snell who introduced the concept of H antigens."[1] Snell's work in mice led to the discovery of HLA, the major histocompatibility complex, in humans (and all vertebrates) that is analogous to the H-2 complex in mice. Recognition of these key genes was prerequisite to successful tissue and organ transplantation.

Snell died in Bar Harbor, Maine on June 6, 1996. His wife died in 1994.