Comprehensibility, or ease of understanding, has emerged as an important construct in second language (L2) speech research. Many studies have examined the linguistic features that underlie this construct, but there has been limited work on behavioral and affective predictors. The goal of this study was therefore to examine the extent to which anxiety and collaborativeness predict interlocutors' perception of one another's comprehensibility. Twenty dyads of L2 English speakers completed three interactive tasks. Throughout their 17-minute interaction, they were periodically asked to evaluate their own and each other's anxiety and collaborativeness and to rate their partner's comprehensibility using 100-point scales. Mixed-effects models showed that partner anxiety and collaborativeness predicted comprehensibility, but the relative importance of each predictor depended on the nature of the task. Self-collaborativeness was also related to comprehensibility. These findings suggest that comprehensibility is sensitive to a range of linguistic, behavioral, and affective influences.