Following the Bombardment of Brussels by the French in 1695, Janssens was commissioned to produce a number of paintings for the Brussels Town Hall to replace those destroyed during the attack on the city. He also worked for the local guilds and churches. He gained a solid reputation and became well-off. He was appointed the court painter of Emperor Charles VI of Austria and resided in Vienna from 1719 to 1722. On the recommendation of the Empress, the widow of Emperor Joseph I, he spent several years in London.