This paper contributes to current sociolinguistic research on the rapidly-changing landscape of digitally mediated communication (Androutsopoulos and Staehr 2018) by presenting mediagrams, a new method for research on transnational mediated interaction. Based on an ethnographic study of mediated multilingual communication in four families with Senegalese-background living in Norway, we develop a visualisation scheme for the documentation and analysis of individual mediational repertoires. Starting with a review of visualisations used in relevant research and an outline of the context of our study, we present the production of mediagrams as a collaborative research process and their subsequent use in further data collection and analysis. Based on participants' language portraits, media maps, and self-selected excerpts of digital conversations, the collected data is coded and visualised in graphs that represent individual networks of interlocutors, language choices, language modalities, and media channels. Follow-up interviews lead to amended versions of mediagrams, which eventually form the basis for the analysis of individual mediational repertoires. In concluding we assess mediagram research as a contribution to citizen sociolinguistics (Svendsen 2018) and discuss blind spots of the method and its potential for wider application.