Many rivers in the Balkan Peninsula are recognised at the European level for the biodiversity they host and their strong cultural heritage. However, they are experiencing significant anthropogenic changes, where their biodiversity and cultural values are often not considered in decision-making. While research has studied the biodiversity of rivers in the Balkans, very little has been done to assess their cultural and social values. The goal of my research was to evaluate people’s perception of the importance of cultural ecosystem services (CES) of the Sava river. I used a combination of participatory methods, engaging the public at different stages, from semi-structured interviews to an online participatory mapping and questionnaire. The evaluation of the CES revealed the general high importance of the six CES considered for the participants. The participants’ valuation of the CES was influenced by certain social characteristics, such as location of residence and gender. ‘Contact with nature’, ‘recreation and tourism’ and ‘nature beauty’ were perceived the most important CES and were also most frequently mapped. Participatory mapping showed that certain services can be experienced together and several hotspots of CES were identified. Recreational facilities, accessibility, protected areas, and certain river hydromorphological features (such as sand banks) were found to influence the spatial distribution of the CES. Finally, my approach showed the advantages of using an online approach to evaluate and map the CES. It allowed me access a significant sample of participants in a limited period of time and interact with citizens to gain deep understanding of their perceptions of the CES. However, this approach also highlighted strong challenges.