Different disciplines have, over time, looked at trust from different standpoints and orientations. In rhetorical studies, trust is closely linked to the Aristotelian concept of ethos, one of the three artistic proofs (ethos, pathos, logos). The concept of rhetorical ethos invites us to reflect on the character of a speaker through the conceptual lenses of virtue, practical judgment, and goodwill to audiences. In this chapter, specifically, we conceptualise the ethos of science as a source of trust. Through a concise overview of some modes of public communication of science before and during the COVID-19 pandemic, we argue for an integrated rhetorical ethos for public scientists dealing with the crises of our times. This notion of scientific ethos recognises the rhetorical citizenship of scientists as key when experts exit the technical sphere and engage lay people in public forums (Pietrucci and Ceccarelli in Rhetoric & Public Affairs 22(1):95–128, 2019). After reviewing the integrated ethos of the scientist citizen, we also discuss the challenges and opportunities of taking up a scientist activist expert stance and we conclude by encouraging public experts to cultivate a deeper awareness of the rhetorical contexts in which they go public in order to promote different types of public agency in times of crisis.