Born at Nancy in France, Jacob served with the Free French forces during World War II. Although badly wounded, he resumed his medical studies in 1945, obtaining his MD from the University of Paris in 1947. In 1950 he became André Lwoff's assistant at the Pasteur Institute, Paris, and, with Elie Wollman, began working on the bacteria, discovered by Lwoff, that carry a nonvirulent virus incorporated in their genetic material. In 1961 they introduced the term ‘episomes’ for genetic elements that become established in bacterial cells. Jacob and Wollman also studied conjugation in bacteria, the process by which genetic material is transferred from one cell to another. They found that the genes of the donor cell enter the recipient cell in a specific order and by interrupting the process, the position of given genes on the chromosome could be determined.

In 1958 Jacob began collaborating with Jacques Monod and Arthur Pardee on the control of bacterial enzyme production, research that culminated in a greatly increased understanding of the regulation of gene activity. In 1960 Jacob and Monod proposed the existence of the operon, consisting of an operator gene and structural genes that code for the enzymes needed in a given biosynthetic pathway. When the enzymes are not required another gene outside the operon, the regulator gene, produces a protein that binds with the operator and renders the operon ineffective. Jacob and Monod received the 1965 Nobel Prize for physiology or medicine for this research, sharing the award with Lwoff.

From 1964 until 1991, Jacob occupied the chair of cellular genetics at the Collège de France; the chair was created in his honor. He became a foreign member of the Royal Society in 1973 and a member of the Academy of Sciences, Paris, in 1977. He also wrote on some of the wider implications of biology in The Possible and the Actual (1981) and has published an autobiography, The Statue Within (1987).