During much of his tenure as senator and his first term as Second Mayor, Hamburg was a fully sovereign country, while after 1871, the First Mayor as head of state of republican Hamburg was equal to the federal princes (Bundesfürsten) within the German Empire.

He belonged to the Hanseatic Berenberg-Gossler banking dynasty and was a son of the banker and senator Johann Heinrich Gossler (1775–1842), co-owner of Joh.

His side of the family was stripped out of their Bank stock and sent to exile to Latin America.

Hermann Gossler studied law at the University of Heidelberg, and worked as a lawyer in Hamburg from 1826 to 1837.

He was the father of Emilie (Emmy) Helene Gossler (1838–1910), married to banker Georg Heinrich Kaemmerer.