Hermanus Koekkoek studied painting with his father, seascape painter Johannes Hermanus Koekkoek. He succeeded his father as a seascape painter when his older brother Johannes Koekkoek died in 1831. In 1831, the family moved from Middelburg to Durgerdam on the Zuiderzee, and then Hermanus moved to Amsterdam in 1832 or 1833. In 1832 he participated in the Leevende Meesters exhibition in Amsterdam, thus showing that his left-handedness did not hinder his talent. Shortly thereafter, he established himself as an independent artist.
Hermanus was the youngest and most famous of the four founding brothers of the Koekkoek dynasty of artists (Koekkoek Barend Cornelis, Koekkoek Marinus Adrianus, Koekkoek Johannes).
The works of the family of artists are scattered throughout the museums of the world.