Effective strategies to enhance the competence of practising health professionals are limited. Communities of Practice are proposed as strategy, yet little is known about their ability to develop cultural competency and practice. This study aimed to measure the impact of a Community of Practice on the self-assessed cultural competency and change to practice of dietitians working in Aboriginal health. A mixed-method approach including a quantitative 16-item cultural-competency self-assessment tool (completed at baseline and after 12 months of participation) together with the qualitative most significant change stories were used. Quantitative and qualitative data were compared together for congruence and difference. All participants (n = 13) completed the cultural competency-self assessment and participated in the significant change story development. They reported that through networking and joint problem solving they increased competence (13 of 16 performance indicators) and qualitative described increased self-confidence for their work in Aboriginal health through improved understanding of the factors related to the impact of history, culture and utilisation of resources on service delivery, appropriate communication strategies, effective relationships and managing conflict. These findings suggests that formalised and structured Communities of Practice may be an effective workforce development strategy to influence the practice of health professionals working in Aboriginal health.