Do political identities influence workers’ willingness to cooperate at work? Do workers prefer copartisans over outpartisans as colleagues even at the expense of competence? This article introduces a novel theory of how political identities permeate modern workplaces in knowledge economies, where collaboration and noncognitive skills are crucial. An original survey experiment conducted in the United Kingdom reveals that workers prefer to avoid working closely with outpartisans and favour collaborating with copartisans. While highly competent workers are generally preferred over less competent ones, their favorability significantly declines if they are outpartisans. A new measure of affective polarization at work, which exploits open-ended survey items, suggests that some individuals perceive partisan and Brexit identities to signal relevant information about non-cognitive skills they highly value in colleagues. More broadly, this article contributes to our understanding of the challenges to workplace cooperation in knowledge economies with significant levels of affective polarization.