The present study explores whether ideological heterogeneity or mass opinion polarization are negatively associated with dimensions of social cohesion, namely social trust and solidarity. Contrary to many scholars, I argue that heterogeneity per se does not damage social cohesion, but in light of ideological opinion polarization, people’s trust and solidarity declines. Using data drawn from the European Social Survey (2002–2014), macro as well as multi-level analyses are conducted. Empirical results confirm the assumptions. Ideological dispersion within the society does not show any effect, neither on general social trust nor on solidarity, whereas ideological opinion polarization negatively affects both, trust and solidarity. In sum, social cohesion is not threatened by simple ideological pluralism, but by an ideological divide of the society.