He was born in Arnhem, the eldest son of Ernst Casimir of Nassau-Dietz and Sophia Hedwig of Brunswick-Lüneburg, and, like his father, died in battle.

The English representative, Sophia Hedwig being the niece of the queen Anne of Denmark, was Sir Edward Cecil.

He brought gifts of a cupboard of gilt plate, a diamond necklace with a locket, horses, and an embroidered petticoat for Sophia Hedwig.

A week later, he was involved in the Capture of Maastricht, along with his cousin, Frederick Henry, Prince of Orange.

Henry Casimir was wounded in Sint Jansteen at the battle of Hulst on 12 July 1640.