Porter was educated at the university in his native city of Liverpool and at Cambridge University, where he was a pupil of Frederick Sanger. After working at the National Institute of Medical Research from 1949 to 1960 he moved to the chair of immunology at St. Mary's Hospital, London. Porter remained there until 1967 when he accepted the post of professor of biochemistry at Oxford.

In 1962 Porter proposed a structure for the important antibody gamma globulin (IgG). Ordinary techniques of protein chemistry revealed that the molecule is built up of four polypeptide chains paired so that the molecule consists of two identical halves, each consisting of one long (or heavy) chain and one short (or light) chain.

Further evidence was obtained by splitting the molecule with the enzyme papain. This split IgG into three large fragments, two similar to each other known as F_{a b} (fragment antigen binding) and still capable of combining with antigen, and a crystalline fragment known as F_c (fragment crystalline) without any activity. This immediately suggested to Porter that, because crystals only form easily from identical molecules, the halves of the heavy chain that make up the F_c fragment are probably the same in all molecules. Thus the complexity is mainly in the F_{a b} fragments where the combining sites are found.

Linking such insights with results obtained by Gerald Edelman and data derived from electron microscopy allowed Porter to propose the familiar Y-shaped molecule built from four chains joined by disulfide bridges with the variable combining part at the tips of the arms of the Y.

In 1972 Porter shared with Edelman the Nobel Prize for physiology or medicine for their work in determining the structure of an antibody.