The first years of Joostens' stay in Spain were characterized by a focus on the improvement of the Belgian-Spanish economic relations. Joostens was for example very active in the preparations of the Spanish pavilion at the world's fair in Liège in 1905. During his Spanish years, Joostens would also be again in the center of the imperialist world theater. Spain was after all an important imperial power and the neighbourhood of Morocco posed both a lot of opportunities and problems. Joostens was first active in the Belgian imperialist penetration of Morocco through the establishment of Belgian companies in the country. Following the First Moroccan Crisis Joostens was appointed by Leopold II to attend the Algeciras Conference together with . The international meeting was installed to figure out a solution for the German contestation of the growing French and Spanish control over Morocco. Leopold II told Joostens that he was not allowed to gain any profits for Belgium at the conference and Joostens loyally followed these orders.