In an era of digital fragmentation and contested expertise, mediated public trust is under pressure. This study examines how journalists in Germany, Italy, and Lithuania perceive their role amid structural media shifts, politicized environments, and the rise of alternative sources. Drawing on 14 focus group discussions and 8 narrative interviews, we explore how national media systems and professional cultures shape journalistic strategies. Rather than a uniform erosion of trust, journalists report polarization shaped by ideology, platform dynamics, and shifting audience expectations. Many strive to act as trust brokers but face constraints from precarious working conditions, editorial pressures, and fragmented publics. We argue that trust in science journalism depends not only on journalistic practice but on broader systemic conditions, including institutional support, media infrastructures, and audience trust cultures (i.e., prevailing trust norms among different publics). This cross-national comparison advances a more differentiated understanding of how trust is negotiated in contemporary science communication.