This paper contributes to the debate on value change by advancing a new explanation of the relationship between political parties and generational-based values in advanced industrialized nations. Through multivariate analysis of World Values and other survey data from 29 countries, we show that the relationship between generations and values tends to vary between polities dominated by major parties and those in which many parties achieve electoral success. Green parties enhance the uptake of postmaterialist values and speed the decline of materialist ones, particularly among younger generations, by promoting a political discourse and agenda that contributes to the formative experiences underpinning value change. This research suggests that institutional structures and political parties need to be given far greater prominence in theories of postmaterial value change.