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. He married Luise Oettinger, a spectroscopist and fellow researcher in 1929. (Luise Herzberg, died in 1971.)