Todd became the Sir Samuel Hall Professor of Chemistry and Director of the Chemical Laboratories of the University of Manchester in 1938, where he began working on nucleosides, compounds that form the structural units of nucleic acids (DNA and RNA). In 1949, he synthesized adenosine triphosphate (ATP) and flavin adenine dinucleotide (FAD).
In 1955, he clarified the structure of vitamin B12, subsequently working on the structure and synthesis of vitamin B1 and vitamin E, the anthocyanins (the pigments of flowers and fruits) from insects (aphids, beetles) and studied alkaloids found in cannabis. He served as chairman of the British government's advisory committee on scientific policy from 1952 to 1964.
He was awarded the Nobel Prize for Chemistry in 1957 for his work on the structure and synthesis of nucleotides, nucleosides, and nucleotide coenzymes. He was knighted in 1954 and raised to the Peerage as Baron Todd of Trumpington in 1962.