Theodore played a growing role in royal governance in the 1240s. Evidence from his writings, documents, and seals allows us to gain a better understanding of this key aspect of his life in his twenties. The chapter reconstructs his responsibilities – fiscal, judicial, managerial, and other – in a power-sharing arrangement with his father. The division of duties between the senior and the junior emperor was a sign of the challenges the empire of Nicaea faced at a time of rapid territorial expansion and the rise of the Mongol menace from the East. Letters and other works of Theodore Laskaris give unique insights into practices of governance and aspects of Nicean society and the economy.