Maass received a Bachelor of Arts degree from McGill University in 1911. Eight years later he was given a Doctor of Philosophy degree from Harvard University.
Maass joined the McGill University in 1920 and became a Macdonald Professor of Chemistry at the same university in 1923, where he worked until his retirement in 1955. He was also a chairman of the department of chemistry at McGill University in 1937-1955.
Also in 1940, Otto took a position of a director general of the Pulp and Paper Research Institute of Canada and held it for fifteen years. In addittion, he worked as an assistant to the president at National research council in 1940-1946. The same years he served as a director of the Directorate of Chemical Warfare and Smoke and chairman of various governmental committees during the Second World War.
Maass was a member of the Royal Society, the Royal Society of Arts, the Royal Society of Canada Chemistry and the Canadian Institute of Chemists.
On June 10, 1926 Otto Maass married Carol E. Robertson.