Throughout healthcare, including education, the need for voicing of concern by speaking up is a globally recognized issue that has come to the fore in the last ten years. There has been a rapid growth in the number of review articles on the topic. To prevent diffusion of knowledge and support future research it is necessary to gather the existing knowledge in a single place. The purpose of the present article is to bring together the existing reviews on speaking up to create a source of unified knowledge representing the current "State of the Art" to advance future research and practice. A State-of-the-Art review was conducted to synthesize the existing knowledge on speaking up. Six databases were searched. Fourteen review articles spanning 2012 to 2021 were identified. Five main research questions have been investigated in the literature and five common recommendations for improvement are made, the knowledge across all reviews related to the research questions and recommendations was synthesized. Additionally, simulation-based research was frequently identified as an important though limited method. Further issues in the literature are identified and recommendations for improvement are made. A synthesis was successfully developed: knowledge about speaking up and research related to speaking up is in an emergent state with more shortcomings, questions, and avenues for improvement than certitude. The whys and how of speaking up remain open questions.