Discourse particles specify how interlocutors’ understandings converge and differ, and appropriate use requires ability to represent propositions from two perspectives simultaneously. This makes discourse particles a highly useful case for investigating developments in children’s ability to monitor and compare mental states, a controversial issue in child language research. Being neither salient, nor obligatory, the particles further allow us to assess children’s motivation to look for interpersonal meanings without strong linguistic incentives. By means of a corpus analysis of peer group conversations (123 hours, 19 children: 1;9–6;3 years), the present study examines at which ages Danish kindergarteners demonstrate stable mastery of the interpersonal contextual demands of five particles marking shared knowledge, disagreement and differential access to knowledge. As background for evaluating children’s particle use as well as order of occurrence, adult consensus on particle meanings was substantiated with a gap-filling test and relative input frequency estimated in caregiver speech. Children were significantly above chance in producing intersubjective particles in felicitous contexts and differentiated clearly between the particles. While there was a strong increase in token frequency over the kindergarten years, children evidenced sensitivity to context from their first productions, and particle felicity did not improve significantly with higher age or production experience. The results suggest that 3-to-6-year-olds routinely monitor and compare representational states, and that they are highly motivated to coordinate conversations as joint actions by pointing to interlocutor perspectives.