This paper analyses the work of photographer Rudolf Mosinger who was one of the most important photographers of the end of the 19th century and the beginning of the 20th. In that period Rudolf Mosinger made plenty of very interesting and valuable photographs which weren't analyzed, interpreted, and valued in detail in the history of Croatian photography. In the first part of the paper, we analyze the current bibliography and historical documents about Rudolf Mosinger and we offer a short history of his life and work in the ateliers in Zagreb which he founded and lead. We also consider the technical devices he used and the advertisements used for the popularization of his photographic manufacture. The paper is further organized according to the motives of Mosinger's photographs. Among them prevail the portraits which have the special function at the turn of the 20th century. The portraits consist of the representations of torsos of full figures, the portraits of children which were quite popular at that age, and the group portraits which represented different collectives – families or members of certain institutions or associations. Rudolf Mosinger was also distinguished as the photographer of the city, and his vedutas captured the development of Zagreb and its important buildings. Mosinger also photographed the environment close to Zagreb, which is shown on his landscapes, in number less than the vedutas. We then analyze Mosinger's photographs from the Millennial exhibition held in 1896. in Budapest. He photographed the motives from Zagreb and Varaždin county and with other photographers represented Croatian areas. In the paper, we also analyze the part of Mosinger's oeuvre developed in cooperation with Salamon Berger, the director of the Ethnographic Museum, where Mosinger's photographs popularized the Croatian folk costumes. The conclusion values the work of Rudolf Mosinger as an important photographer in the history of Croatian photography.