Does an increasing divide in normative notions within a population influence citizens’ political protest behaviour? This article explores whether public opinion polarisation stimulates individuals to attend lawful demonstrations. In line with relative deprivation theory, it is argued that in an environment of polarisation, individuals’ normative notions are threatened, increasing the probability that they will actively participate in the political decision‐making process. Using the European Social Survey from the period 2002–2014 and focusing on subnational regions, multilevel analyses are conducted. Thereby a new index to measure public opinion polarisation is introduced. Depending on the issue, empirical results confirm the effect of polarisation. While average citizens are not motivated to demonstrate over the issue of whether people from other countries are a cultural threat, they are motivated by the issues of reducing inequality and of homosexuality. The article goes on to examine in a second step whether ideological extremism makes individuals more susceptible to environmental opinion polarisation. Findings show that members of the far left are more likely to protest when their social environment is divided over the issue of income inequality. In contrast, members of the far right are motivated by rising polarisation regarding homosexuality. In sum, citizens become mobilised as their beliefs and values are threatened by public opinion polarisation.