This paper discusses the epistemic value of political parties and other partisan associations from the standpoint of epistemic democracy. It examines whether political parties contribute to the quality of democratic deliberation, thus increasing the epistemic value of democratic decisionmaking procedures, or represent a threat that polarizes the society and impedes and distorts the public deliberation. The paper introduces several arguments that support the epistemic value of partisanship. Partisan associations empower otherwise marginalized social groups or groups that have disproportionally small political influence by facilitating political education or by connecting citizens and experts who share the same values. Partisan associations also help us resist the epistemically damaging effects of hermeneutical (epistemic) injustice by enabling marginalized citizens to construct alternative discourses. However, though partisanship might facilitate the transmission of knowledge, this deliberative tool will only be used in a group of like-minded citizens (i.e. within a political party), thus increasing the polarization between the parties and citizens alike, and decreasing the epistemic value of such collective decision-making procedures. The paper analyses some epistemic strategies (like red-teaming or building a critical thinking culture) that can help us avoid or (at least) reduce the epistemically damaging effects of polarization. However, internal action (from within a deliberative group) might not be enough. Making the deliberation on political issues public and spreading it through different forms of citizens’ organizations will ensure that political deliberation is not closed within a single homogenous deliberating group (i.e. the party). These practices should significantly reduce the damaging effects of group polarization.