The present study aimed at investigating Turkish high school students' metacognition and its relation to achievement goals (mastery approach goals, mastery avoidance goals, performance approach goals, performance avoidance goals), perceived competence, and perceived classroom environment (challenge and threat). Metacognition was examined in terms of knowledge of cognition (declarative knowledge, procedural knowledge, and conditional knowledge) and regulation of cognition (planning, information management, monitoring, debugging, and evaluating). Self-report instruments were administered to 141 high school students with a mean age of 15.29 to assess variables of the study. Results reveal that Turkish high school students have more declarative and conditional knowledge than procedural knowledge and mostly use debugging strategies. All motivational variables except threat were found to be positively linked to students' metacognition. The students also appear to adopt approach goals more than avoidance goals. Results were interpreted taking the Turkish educational system into consideration.