Objectives: To describe the current knowledge and practice of sarcopenia diagnosis and treatment among health-care professionals before, directly after and 6 months after a professional development event on sarcopenia. Methods: This longitudinal study included Australian and New Zealand health-care professionals who completed questionnaires on knowledge, practice and barriers regarding sarcopenia before, directly after and 6 months after attending a professional development event on sarcopenia. Results: A total of 250 professionals participated; 84 completed the 6-month questionnaires. Before, directly after and at 6 months, respectively, 14.7%, 93.4% and 59.5% identified sarcopenia as a disease; 2.0%, 79.6% and 38.1% correctly answered the sex-specific cut-offs for low handgrip strength. Respectively, 12.0% and 14.3% reported to make sarcopenia diagnoses as part of their practice before and at 6 months. Conclusions: Knowledge about sarcopenia is limited among health-care professionals who attended a professional development event. Retention of knowledge remains a challenge to be addressed.