Unidad de excelencia María de Maeztu MdM-2015-0552 There is a deeply relational aspect to the systems people employ for sorting through and prioritizing plural values assigned to social-ecological interactions. Spurred by interpersonal relationships and adhesion to societal core values, such as justice and reciprocity, relational values go beyond instrumental and intrinsic approaches to understanding human behaviour vis-à-vis the environment. Currently, this relational dimension of values is entering the spotlight of the cultural ecosystem services (CES) literature focusing on non-material benefits and values people derive from ecosystems, such as aesthetics and sense of place. Relational values foster reflections on appropriateness and morality of preferences and respective behaviours in contributing to collective flourishment across space and time, holding implications for social-ecological justice and sustainability. Recently, several studies explored the potential of using social media data for assessing values ascribed to CES, but did not look at how this emerging approach could contribute to an enhanced understanding of relational values. In order to take up this goal, we conducted a systematic review, screening 140 publications and selecting 29 as relevant for exploring the extent to which relational CES values are inferable through social media. Our results show that social media data can reveal CES values' plural and relational dimension. Social media platforms, thus, can be understood as new arenas for the co-construction of values, where relational values stemming from social-ecological interactions are negotiated and defined. Yet, work on their implications for social-ecological justice and sustainability needs to be extended.