Herzberg was born in Hamburg, Germany on December 25, 1904 to Albin H. Herzberg and Ella Biber. He had an older brother, Walter, who was born in January 1904. Herzberg started Vorschule (pre-school) late, after contracting measles. Gerhard and his family were atheists and kept this fact hidden. His Father died in 1914, at 43 years of age, after having suffered from dropsy and complications due to an earlier heart condition. Herzberg graduated Vorschule shortly after his father's death.. His wife died in 1971.

Initially, Herzberg considered a career in astronomy, but his application to the Hamburg Observatory was returned advising him not to pursue a career in the field without private financial support. After completing high school at the Gelehrtenschule des Johanneums, Herzberg continued his education at Darmstadt University of Technology with the help of a private scholarship. Herzberg completed his Dr.-Ing. degree under Hans Rau in 1928.

Herzberg's most significant award was the 1971 Nobel Prize in Chemistry, which he was awarded "for his contributions to the knowledge of electronic structure and geometry of molecules, particularly free radicals". During the presentation speech, it was noted that at the time of the award, Herzberg was "generally considered to be the world's foremost molecular spectroscopist."

Herzberg authored some classic works in the field of spectroscopy, including Atomic Spectra and Atomic Structure and the encyclopaedic four volume work: Molecular Spectra and Molecular Structure, which is often called the spectroscopist's bible. The three volumes of Molecular Spectra and Molecular Structure were re-issued by Krieger in 1989, including extensive new footnotes by Herzberg. Volume IV of the series, "Constants of diatomic molecules" is purely a reference work, a compendium of known spectroscopic constants (and therefore a bibliography of molecular spectroscopy) of diatomic molecules up until 1978.

Herzberg was honoured with memberships or fellowships by a very large number of scientific societies, received many awards and honorary degrees in different countries. The NSERC Gerhard Herzberg Canada Gold Medal for Science and Engineering, Canada's highest research award, was named in his honour in 2000. The Canadian Association of Physicists also has an annual award named in his honour. The Herzberg Institute of Astrophysics is named for him. He was made a member of the International Academy of Quantum Molecular Science. Asteroid 3316 Herzberg is named after him. In 1964 he was awarded the Frederic Ives Medal by the OSA. At Carleton University, there is a building named after him that belongs to the Physics and Mathematics/Statistics Departments, Herzberg Laboratories. Herzberg was elected a Fellow of the Royal Society (FRS) in 1951.