This mixed method case study examined potential influences of social agents or immediate environments on individuals' metacognition. Via quantitative methodologies, 122 pre-service teachers' metacognition was measured by the Turkish Metacognitive Awareness Inventory, and metacognitive components did not show any variations across majors, locations of previous studies, the highest degree of education in the family, frequently communicated friends, and regions. Regression analyses revealed that friends were a significant predictor for metacognition. Also, focus group interviews were analyzed thematically via deductive codes regarding the theory of metacognition. Findings confirmed that friends may support individual metacognition at all levels, metacognitive knowledge, regulation, and experiences through cooperation, modeling, reflections, discussions, feedback, and peer evaluation. Pre-service teachers' engagement on the social media may also support their regulatory strategies due to models' task performances or by their reflecting upon those performances. Teachers and family may support metacognitive knowledge, specifically career goals via expectations, anecdotes, and experiences. On the other hand, schools and the Turkish culture may impose some limitations on the youth, and they may engage in reflection and self-questioning to manoeuvre negative experiences or conflicts. Thereby, cross-national and longitudinal studies are highly suggested to explicate the social foundations of metacognition.