Wieland was born in Pforzheim, Germany, the son of a chemist in a gold and silver refinery. He was educated at the University of Munich where he obtained his PhD in 1901. After teaching at the Munich Technical Institute and the University of Freiburg, Wieland succeeded Richard Willstätter in 1925 as professor of chemistry at the University of Munich, a post he retained until his retirement in 1950.

In 1912 Wieland began work on the bile acids. These secretions of the liver had been known for the best part of a century to consist of a large number of substances. He began by investigating three of them: cholic acid, deoxycholic acid, and lithocholic acid, finding that they were all steroids, very similar to each other, and all convertible into cholanic acid.

As Adolf Windaus had derived cholanic acid from cholesterol, an important biological sterol, this led Wieland to propose a structure for cholesterol. For his contributions to steroid chemistry Wieland was awarded the 1927 Nobel Prize for chemistry.

After 1921 Wieland worked on a number of curious alkaloids including toxiferin, the active ingredient in curare, bufotalin, the venom from toads, and phalloidine and amatine, the poisonous ingredients in the deadly amanita mushroom.