The United Nations (UN) considers sports as an important enabler of sustainable development. The popular and fast-growing Participatory Sports Event (PSE) sector can play an important role in this regard, however, research that measures and reports sustainability in PSEs is scarce. Therefore, the aim of this paper was to construct and validate a research instrument based on the UN’s sustainable development goals, and to examine sustainability in PSEs. To this end, an online survey was administered among a representative sample of 303 PSE organisers, located in Flanders, Belgium. A confirmatory factor analysis affirmed the social, economic and environmental dimensions of the instrument and provided evidence for its validity and reliability. The results reveal significant discrepancies between the three dimensions, with a noticeable lower score for environmental sustainability compared to social and economic sustainability. Furthermore, challenges are highlighted in the field of the civil society sector and in walking sports events. The findings also indicate that large-sized events are more likely to be sustainable. The current study can act as a foundation for future research on sustainability in PSEs and can assist PSE organisers and policymakers to increase the sustainability-related performance of the sector.