This master thesis will deal with issues of Senj's economic history during the 17th century, more precisely the time between the Peace of Madrid and the Peace in Srijemski Karlovci (1617-1699). Within studying Senj’s economic history as its narrow field of work I will analyze specific type of trade which was developed due to the needs of the local population to continue dealing with their most important branch of industry, namely intermediary trade. Furthermore, the subject of research on economic specifics will cover the early modern city on two levels: Senj as a free royal city and Senj as a military border captaincy. In other words, the work will include research into the economic possibilities of the civilian population, in which Senj merchants, ship owners, seafarers, and all those who have the status of citizens according to the Senj Statute can participate. On the other hand, the military aspect of the administration will be considered, as well as attempts of state intervention in the city's economy, first through the captain of the Senj as a representative of the royal government, and then directly by the Habsburg government itself. Also, the paper will be divided into several key chapters and subchapters, starting with political and social opportunities important for understanding the main issue, with emphasis on the aspect of social structure in relation to trade activities, followed by analysis of local trade (town fairs), maritime and intermediary trade. At the very end of the paper, I will briefly examine the economic changes at the end of the century, as well as beginnings of the first external influences of the state government within the framework of the new economic ideas of Habsburg mercantilism.