This study explores early career academics' (ECAs) professional learning in a Danish university's Professional Learning (PL) program, based on problem- and project-based learning (PBL) principles. Using a complexity theory lens, professional learning is viewed as a dynamic process involving intrapersonal, behavioral, relational, and contextual sources. Data from 38 written reflections via a questionnaire and six in-depth interviews were analyzed to assess ECAs' learning outcomes and challenges during and after the PL program. The findings indicate that the program advanced participants' PBL and pedagogical knowledge, changed their pedagogical beliefs and teaching practices, and improved their collaborative skills and interactions with students and colleagues. Several challenges ECAs confronted are reported at individual and organizational levels, namely, time management, the learning process, the actual teaching and supervision process, institutional culture, and resource allocation. The study suggests ways for ECAs, program designers and organizers, and university management in promoting more effective professional development processes.