In this paper, we introduce the PESI project for investigating the interpersonal dynamics of Personality and Emotions in Social Interactions. The final sample in this preregistered study consisted of 436 participants (218 dyads) who were on average 31.2 years old (SD = 14.0, Range: 16–75). The study consisted of three parts and used a multimethod assessment: In Part 1, participants filled out online self-reports of personality. In Part 2, participants interacted in dyads at zero acquaintance in the laboratory and filled out self- and partner-reports of various states. During the interactions, video and audio tracks were recorded simultaneously, allowing later video analyses of every participant. In Part 3, participants provided self-reports via a follow-up online questionnaire. Our aim is to encourage researchers to use the present ideas, open materials, and data to be inspired to conduct future research.