Metacognition has been increasingly discussed as one of the main features of learning in the 21st century (see Haukås, Bjørke, & Dypedahl, 2018). In the Dynamic Model of Multilingualism Theory (DMM) (Herdina & Jessner 2002), which applies Complexity and Dynamic Systems Theory (CDST) to multilingualism, it is argued that multilinguals develop increased knowledge of languages and language learning through experience. In this article a CDST perspective on multilingual learning and teaching with a focus on metacognition will be presented. The central sub-component of metacognition in DMM, in the form of multilingual awareness, comprising metalinguistic and cross-linguistic awareness in multilingual learners, will be discussed as a core feature of multilingual proficiency in multilingual development. In a number of studies in the Austrian and South Tyrolean context multilingual awareness has turned out as a core factor in both learning and teaching. These studies show that multilingual awareness has to be trained in multilingual pedagogical approaches in order to foster multilingualism. A holistic approach is needed to deal with the ongoing tensions between complexity, dynamics, adaptation and stability. Although it becomes clear that the nature of multilingualism can only be understood in relation to its context, it is nevertheless possible to isolate and define constant factors in an efficient multilingual awareness training as provided by the "Five Building Blocks of Holistic Multilingual Education."