The appointment of managers to new positions in Iranian public organizations is invariably accompanied by multiple challenges due to complex bureaucracy, frequent political changes, and diverse stakeholder expectations. This qualitative study, employing an interpretive phenomenological approach, aimed to explore the lived experiences of newly appointed senior managers and to identify their proactive strategies for effective adaptation to new job positions. The participants were 19 senior managers from public headquarters in Mashhad, selected through purposive sampling until theoretical saturation was achieved. Data were collected via in‑depth semi‑structured interviews conducted between August and October 2023 and were coded and analyzed using MAXQDA software. The findings revealed that successful adaptation of newly appointed managers is a self‑initiated and proactive process. Data analysis led to the extraction of seven main themes: (1) organizational environment assessment and analysis, (2) organizational communication and interactions, (3) strategy planning and implementation, (4) personal and organizational development, (5) challenge and risk management, (6) performance and productivity improvement, and (7) external and inter‑organizational networking, along with 21 sub‑themes. Since the proactive strategies of newly appointed managers serve as the key to successful organizational adaptation in the public sector context, they enable managers to reduce role ambiguity, gain social legitimacy, manage internal resistances, and implement constructive changes within bureaucratic government structures. The findings of this study extend organizational socialization from a passive framework toward proactive agency, offering an indigenous model for designing managerial training programs, role transition policies, and leadership empowerment initiatives in the public sector.