Purpose: This study aims to focus on newcomers' learning strategies when they perceive organizational socialization support to be lacking, and on interpersonal characteristics that insiders should possess to support the newcomers' proactive behaviors in this context. Design/methodology/approach: Data were collected through 14 face-to-face, in-depth semi-structured interviews and analyzed with a conventional content analysis method (Paillé and Mucchielli, 2013), involving first a thematic analysis and afterward, a conceptual analysis using MaxQDA11©. Findings: The authors' analysis highlights that when newcomers perceive the formal organizational socialization support as lacking, they regulate their proactive behaviors by seeking indirect guidance, and more precisely, by engaging in informal interactions with insiders likely to help them socialize. These interactions can have a cost in terms of self-image, so newcomers regulate their proactive behaviors by looking for insiders perceived to be psychologically safe, even if they have to look for them in other working contexts. Practical implications: Considering the regulation process of newcomers' proactive behaviors according to their perceptions, human resources management should focus on those perceptions and develop a blended learning approach including formal learning programs, as well as individualized support to facilitate on-the-job learning and respond to personal needs. Special consideration should also be given to interpersonal skills displayed by insiders. Originality/value: The originality of the study is the use of a qualitative methodology focusing on newcomers' main learning strategy according to their perception of organizational socialization support and the psychological safety climate. The limitations of the authors' work are the size of the study population and the fact that part of the interviewees were successfully socialized by reaching 15 months on their new post at the point where the interviews were conducted.