Contemporary conservation professionals are part of a workforce focused on overcoming complex challenges under great time pressure. The characteristics of conservation work, and in particular the evolving demands placed on the workforce, mean that to remain effective these professionals need to enhance their skills and abilities continually. Currently, there are no sector-wide guidelines to promote systematic professional development that addresses both individual and organizational learning. This study builds upon existing knowledge from other sectors by examining professional development in conservation through an in-depth qualitative thematic analysis of interviews with 22 conservation professionals, resulting in an effectiveness framework for professional development in the conservation sector. Our findings indicate how individuals’ motivation to learn, proactivity, open-mindedness towards alternative information and views were considered preconditions for effective professional development. A balance between organizational goals and career ambitions was found essential to maintain this motivation to learn and vital for staff retention and preservation of institutional knowledge. Professional development plans may help distinguish between individual career aspirations and organizational objectives and aid a discussion between staff and management on how to balance the two. Leaders have the opportunity to remove barriers to effective professional development. We discuss solutions to overcome specific barriers, to promote an inclusive approach for diverse learners through provision of opportunities, effective learning design, and resource distribution for professional development. This effectiveness framework can be used by conservationists and conservation organizations to plan and decide on professional development.