Metacognition is the ability to monitor and control one's own cognition and behaviour. However, the role of metacognition in language remains poorly understood. Here we investigated metacognitive processing in non-native language perception and production, by asking participants to rate, on a trial-by-trial basis, their self-confidence in the accuracy in a phoneme identification and production task. The results revealed metacognitive ability in perception, as participants' confidence judgments aligned with the accuracy in the non-native speech discrimination task. In the production task, self-confidence did not align with a fine-grained precision measure of one’s own production - indexed by Mahalanobis distance to the target-vowel native space. However, self-confidence ratings predicted whether one’s production was within/outside the ‘native’ zone, suggesting that metacognitive monitoring in non-native language production operates on relatively coarse, yet meaningful sound level representations. While overall confidence ratings were similar and highly correlated between the perception and production tasks, there were no associations between the two language domains regarding the primary task performance or metacognitive ability. We discuss the ramifications of these findings for domain-generality/specificity in metacognitive processing in non-native language, and the unsettled debate on the relationship between language perception and production. Finally, we note future research directions that emerge from the present work.