This essay argues that union democracy (in the sense of active direct democracy at local levels in combination with highly accountable representative systems at more general levels) can be an important foundation for efforts to build a participatory society. It establishes, through a literature review, that pessimism about the capacity of unions to be functioning democracies is overstated; and then offers corrections for three weaknesses in the classical theory of participatory democracy. The first weakness – failing to analyze how participatory processes are gendered, racialized, and sexualized – is overcome by drawing upon feminist ideas for creating highly inclusive group processes. The second weakness – believing that an exaggerated consensus can be created through participation – is remedied with insights drawn from agonistic pluralism. The third weakness – assuming that participation in workplace governance is the essential, participatory training ground – is corrected with insights drawn from research on deliberative democracy. After enumerating eight reasons to pick unions as a focus for participatory efforts from amongst the various alternatives, the essay concludes with a historical example of how the combination of direct democracy and representative democratic accountability in the five United Mine Workers of America locals in the Crowsnest Pass, Canada, in the mid-20th century “spilled over” into this regional coalfield society, thereby nurturing a fledgling participatory society.