We demonstrate effects of political preferences on interpersonal interactions in the environment of the highly unstable and volatile party system of the Czech Republic. The effects of partisanship on interpersonal relations are compared to the effects of attitudes on a salient issue. Two experiments confirm the potential of political partisanship to affect the individual’s ingroup preferences and outgroup biases, which can influence willingness to converse with others in the context of an unstable party system. In a conjoint experiment, dis/agreement on immigration has comparable effects on interpersonal interactions. Avoidance of interactions with out-partisans is amplified when out-partisans talk about politics often. The patterns of ingroup preferences and outgroup biases are replicated in a trust game experiment. Both partisanship and immigration attitudes influence how subjects interact with others. Given the political context, the study provides a hard test of politically motivated ingroup and outgroup biases stemming both from party and policy preferences.