We illuminate adult learning by two theoretical approaches, conceptual change and metacognition, that have widely inspired the research done on learning and instruction during the past 50 years. Our leading question is how adults learn and how their learning processes can be facilitated in formal or informal learning environments from the perspective of conceptual change and metacognition. Conceptual change refers to learning processes in which an individual intentionally changes her initial understanding concerning counterintuitive science concepts. Metacognition can be seen as a cognitive mechanism which monitors and regulates thinking processes. Thus, traditionally, metacognition is considered to consist of knowledge of cognition and regulation of cognitive processes. It can be suggested that university students need support in metacognition because they experience many conceptual changes during university studies. Especially the characteristics of learning environments improving metaconceptual awareness and so enhancing conceptual change are discussed. Furthermore, pedagogical consequences are drawn for developing teaching and learning practices for adults supporting integrative thinking in adult education.