A growing number of people use social media to seek information or coordinate relief activities in times of crisis. Thus, social media is increasingly used by emergency agencies as well to reach more people in crisis situations. However, the large amount of available data on social media could also be used by emergency agencies to understand how they are perceived by the public and to improve their communication. In this study, we examined the Twitter communication about the German emergency agency “Johanniter-Unfall-Hilfe” by conducting a frequency, sentiment, social network and content analysis. The results revealed that a right-wing political cluster politically instrumentalised an incident related to this agency. Furthermore, some individual persons used social media to express criticism. It can be concluded that the use of social media analytics in the daily work routine of emergency management professionals can be beneficial for improving their social media communication strategy.