A new qualification benchmark, the Qualification and Credit Framework (QCF) Diploma Level 6 in Career Guidance and Development was established in the UK in 2011. This study was conducted to ascertain whether a theoretical nexus is necessary for practice and how this could contribute to the professionalisation of the adult careers sector in England. The study was undertaken with practitioners, all of whom had trained either through the work-based competency route or the academic route. Practitioners were asked to consider their theoretical modalities and how this influenced the embedding of theory within their professional practice. Analysis of survey and case study data revealed that degrees of exposure to theory during initial training affect capacities for theoretical integration during ongoing practice and development.