More and more Europeans acquire a second language (L2) during adulthood. However, people greatly differ in their learning success across different learning settings, such as phone apps or in-class. Due to its key role in acquiring our first language during childhood, social interaction might also play an important and underappreciated role in L2 learning. Nevertheless, understanding the role and underlying processes of social interaction in L2 learning has been hindered so far by an enormous technical hurdle: natural social settings have to be translated into the controlled lab environment. With this project, we aim to use a novel approach, combining social cognition, neurolinguistics and ecological valid virtual reality (VR) to tackle this hurdle for the first time. We will design VR environments in which we can control the type of social interaction and the social agent with whom the participant interacts. This will allow us to determine all relevant factors of social interaction that benefit L2 learning success in a natural, yet controlled setting. Furthermore, we will overcome the challenge of combining the VR experience with simultaneous brain measures in the form of electroencephalography (EEG), as well as psychophysical (pupilometry and eye movements) and behavioral measures. This will enable us to measure the effects of social interaction on different cognitive levels and with different temporal resolutions. Our team associates renowned experts in neurolinguistics, L2 learning, social cognition and VR to ensure this project’s success. Furthermore, we will collaborate with a tech company to translate our results to a marketable product, targeted at immigrants who wish to acquire Catalan and Spanish. In sum, our project combines multiple disciplines and state-of-the-art techniques such as VR and EEG to finally gain insight into what is likely one of the most important drivers of language learning: social interaction.