The study deals with the life story of the younger daughter of Premysl Ottokar II (1253–1278) Agnes (1269–1296) who was married to the youngest son of the Roman King Rudolph I Habsburg (1273–1291). The introduction of the life of the younger royal daughter was initiated by the find of Swiss editions which had not been used in the local historiografy so far and which have brought information about the life of the royal daughter Agnes in the Habsburg family estates. The study introduces the reasons for the marriage between two children, Agnes and young Habsburg, unclear facts regarding her childhood spent in Bohemia and subsequently her departure for the Habsburg family estates. The study brings new information about her life with her husband and mainly after his death when she lived on the Swiss-Schwabian border as a widow on the revenue from her dowry estates. The text emphasizes the fact that Agnes, as a duchess, published deeds, either independently or in the name of her minor son and she placed seals on them.