Nikolaus August was born in August 1831 at Drottningholm Palace, and was the youngest son of Oskar (I) and Josefina of Leuchtenberg. Prince August was Duke of Dalarna.
In 1849-53, he spent time studying in Uppsala. In April 1864, he married Teresia of Saxe-Altenburg. The couple did not have any children.
In 1866 he became a Lieutenant, and had progressed to the rank of General by 1872. August did not share his brothers' talents, but he was a kind-hearted, down-to-earth person with a number of eccentric ways. As a young man, he lived periodically at Stjernsund Castle.
After a period of illness, August died in 1873 at the age of 41 at the Royal Palace of Stockholm.