Policy decision‐making modes in governance contexts have become increasingly participatory. This raises questions about legitimacy, and how to measure this concept. The current article advances a multifaceted measurement of perceived legitimacy of policy decision‐making modes in participatory governance, capturing the three components of legitimacy (input, throughput, and output) with two items each. This six‐item measure was tested in a vignette survey (total N = 4583), which was administered among four types of democratic stakeholders: politicians, civil servants, civil society, and citizens. Respondents completed the scale for four different policy decision‐making modes (representative, consultative, co‐decisive, and decisive). Our six‐item scale shows excellent internal consistency as an encompassing measure, while at the same time also allowing for fine‐grained analyses on difference patterns in the input, throughput, and output components of legitimacy. As such, it provides a relevant and parsimonious tool for future research that requires a multifaceted measurement of the perceived legitimacy of participatory governance.