Jangsam, literally meaning ‘long robe’, was an outer garment worn by women of various social classes during the Joseon Dynasty. However, historical records show considerable confusion regarding its nomenclature, the status of wearers, occasions of use, and its form, which has imposed certain limitations on previous studies. This study, therefore, focuses on the usage contexts and physical forms of Jangsam worn by royal women in the Joseon period. The main findings are as follows. Among royal women, Jangsam was worn by queens, crown princesses, selected royal concubines, princesses, and wives of princes. Jangsam was used for both mourning rites and wedding ceremonies, and it is presumed that the form used for both was identical. The Jangsam worn by royal women is confirmed to have featured a straight collar fastened to the right side. In the late Joseon period, however, Hwalot with a square type collar and symmetrically facing front panels also appear in the records. In records related to funeral rites, mentions of Jangsam as part of the minor and major encoffining suggest family members or relatives likely sent the garments; thus, they cannot be conclusively identified as the deceased’s own attire. Excluding these cases, all such Jangsam were red. A recently excavated early Joseon Jangsam from Byeolnae, Namyangju, features a straight collar fastened to the right side. This artifact is estimated to represent the same form as royal Jangsam up to around the 16th century. In the late Joseon period, red Jangsam evolved into Hwalot. After the 18th century, as confirmed by extant artifacts, it took the typical Hwalot form with a square type collar and symmetrically facing front panels. The 17th century is presumed to represent a transitional phase in this evolution. Based on this observation, three possible patterns of change in the form of the Jangsam from the early to late Joseon period are proposed.