Early career researchers (ECRs) are increasingly socialised in professional environments where science communication is seen as part of their academic role. ECRs respond to these expectations differently, shaped in part by social relationships within and beyond academia. This study uses ego-network interviews with 24 highly communicative STEM (Science, Technology, Engineering, Mathematics) ECRs in Germany to examine how social relationships influence the importance as well as the integration of science communication in their professional identity. Results show that recognition and support often come from private contacts and the science communication community, while workplace environments are perceived as less supportive and formative. Moreover, different formats and processes of science communication seem to be tied to distinct networks and underlying communication motives.