The article discusses the peculiarities of the functioning of Ukrainian fantasy fandom as well as its transformations related to two main aspects: 1) from “the old” fandom to the new one and 2) from the ordinary forms of existence during the peaceful times to existence during the wartime after Russian full-scale invasion in Ukraine in February 2022.The article indicates the general transformation of the scholarly research of the fandom in the Western academic context. It is possible to present it as the flow from an “ethnographic” or external interpretation of the fandom as a part of the mass culture that depends on the specifics of the popular culture production, to the “internal” or integrated descriptions of the fandom functioning as a separated sphere of social activity.The article argues that there are two stages of the existence of Ukrainian fantasy-related fandom. “The old” fandom emerged in the pre-computer era and was based on the Soviet fandom, which influenced its peculiarities. For instance, there are such aspects as statelessness, the absence of national representation (and the dominance of Russo-centrism as the common cultural platform), the importance of direct interpersonal contacts, distancing from contact with authorities, and the tendency to reduce the presence of the fandom in the shared urban space.Unlike “the old” fandom, “the new” one is developing under the influence of new communicational technologies, which erases the barriers to entering the fandom for new members, enlarges the zones of potential contacts, eliminates geographic and territorial barriers, etc. Moreover, “the new” fandom is more integrated into the urban space and is more available for communications. For the Ukrainian fandom, the transition from “the old” fandom to the “new one” means focusing on domestic cultural issues as the fandom becomes Ukraine-centric.Russian military aggression against Ukraine, from annexing Crimea in 2014 to the full-scale invasion in 2022, became the inner catalyst for the development and transformation of the Ukrainian fandom. The external existential threat led to the transformation of the practices, implemented by the fandom and to the rise of the Ukrainian popular culture, which is closely related to the fandom. During the full-scale invasion, the Ukrainian fandom, preserving its core responsibilities (communication and social activity around popular culture functioning), spreads its new topical responsibilities: apart from the domestic volunteer work, which unites the majority of Ukrainian communities, it includes the educational activity, gaining subjectivity during international communication with the foreign fandom of Europe and the USA, charitable activity, etc.