Walter received degree in chemistry (with first-class honors) at Manchester University in 1906, and then Doctor of Science in organic chemistry there in 1911. After that he earned Doctor of Philosophy at University of Goettingen in 1910.
Walter worked for some time from the age of fourteen in the local Ryland's linoleum factory managed by his father.
In 1912 Haworth became a lecturer at United College of University of St Andrews in Scotland and became interested in carbohydrate chemistry. He then began studies on the structural features of the disaccharides. Haworth organised the laboratories at St Andrews University for the production of chemicals and drugs for the British government during World War I. He was appointed Professor of Organic Chemistry at the Armstrong College in Newcastle upon Tyne of Durham University in 1920. The next year Haworth was appointed Head of the Chemistry Department at the college.
In 1925 he was appointed Mason Professor of Chemistry at the University of Birmingham and held thet position until 1948. Among his lasting contributions to science was the confirmation of a number of structures of optically active sugars: by 1928, he had deduced and confirmed, among others, the structures of maltose, cellobiose, lactose, gentiobiose, melibiose, gentianose, raffinose, as well as the glucoside ring tautomeric structure of aldose sugars.
Walter also developed a simple method of representing on paper the three-dimensional structure of sugars. The representation, using perspective, now known as a Haworth projection, is still widely used in biochemistry.
In 1922 Walter married Violet Chilton Dobbie, daughter of Sir James Johnston Dobbie. They had two sons, James and David.