At the age of fourteen, he was apprenticed to a master decorative painter and began to take drawing lessons at the Royal Danish Academy of Fine Arts.

[3][4] After a successful showing at the Charlottenborg Spring Exhibition in 1827, he turned to sculpture and received some orders, including one for reliefs in a hall at Christiansborg.

In 1830, he was awarded a gold medal for his relief of Christ healing the sick, which is now displayed at Kongens Nytorv public square in Copenhagen.

[5] By 1834, having failed to reproduce this initial success, he requested a loan from Privy Councilor Nicolai Abraham Holten, who had recently bought an altarpiece Simonsen had been unable to sell after those who ordered it changed their minds.

[8] From 1848 to 1851, during the First Schleswig War, he concentrated on large canvases of military scenes, several of which were acquired for the Royal Collection.

He once again focused on battle painting during the Second Schleswig War and became a member of the Royal Swedish Academy of Arts.