Doctors and teachers in their first year of practice face steep learning curves and increased stress, which can induce poor mental health, burnout and attrition. Informal workplace support from colleagues can help smooth transitions and aid professional development. A three-phase comparative research design was used to explore who provides informal workplace support to early-career professionals, types of support and influencing factors. Phase 1 was a systematic secondary analysis of interviews and audio diaries from 52 UK doctors in their first year of foundation training (F1s). Phase 2 involved new narrative interviews with 11 newly qualified teachers (NQTs) from English secondary schools. Phase 3 was a comparative analysis to produce a model of workplace support. Given barriers to accessing senior doctors, F1 doctors drew upon nurses, pharmacists, microbiologists, peers/near-peers and allied healthcare professionals for support. NQTs gained support from allocated mentors and seniors within subject departments, as well as teaching assistants, allied support staff and wider professional networks. Support types for both professions included information and advice on practice, orientation to local settings, collaborative development activities, observation and feedback, and socioemotional support. Influencing factors included variable departmental cultures, limited opportunities for informal contact, sometimes negative inter-group perceptions and the agentic responses of novices. The resulting workplace model of support could underpin future research and evaluations of support in similar 'hot-action' environments. In medicine and teaching, greater utilisation of near-peers and allied staff, improved role understanding and communication, increased informal contact and sharing successful strategies across professions could enhance supportive relationships.