BackgroundTo deliver high-quality care for individuals with complex medical conditions, residents need to be trained across the boundaries of their specialties. This study aimed to explore learning activities and influencing factors in intraprofessional workplace learning by residents in complex tertiary care.MethodsThis qualitative study was conducted in a tertiary care children’s hospital. In September – December 2017, fourteen individual and two focus group interviews were conducted with a purposive sample of residents and supervisors of various specialties. Transcribed interviews were thematically analyzed to describe learning activities and influencing factors that play a role in intraprofessional workplace learning in complex tertiary care settings during residency training.ResultsRespondents described numerous activities that they considered opportunities for intraprofessional learning, both directly and not directly related to patient care. However, deliberate attention to intraprofessional learning often seemed to be lacking in clinical practice. Influencing factors on a system (macro), organization (meso) and personal and interpersonal level (micro) level were identified. Factors on the macro and meso level mainly determined whether intraprofessional learning opportunities arose, while micro level factors mainly influenced whether opportunities were seized.ConclusionsThere are ample opportunities for intraprofessional workplace learning in complex tertiary care for residents. Residents may benefit more from intraprofessional learning opportunities if these are made more intentional and deliberate. Influencing factors at the macro, meso and micro level provide targets for interventions aimed at enhancing intraprofessional workplace learning in postgraduate medical training.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12909-023-04363-5.