The present study investigated six experienced English as a second language (ESL) teachers' metalinguistic knowledge of the English intonation system through analysis of their metalanguage. Participants' metalanguage related to intonation was collected while completing three tasks: (1) a semi-structured interview, (2) a simulated teaching demonstration, and (3) a pronunciation needs assessment. Qualitative content analysis revealed information related to their metalinguistic knowledge of the intonation subsystems of parsing, prominence, and pitch contour. Although broad patterns of metalinguistic knowledge across participants were evident, metalanguage variation showed individual differences in conceptualization and descriptiveness of the subsystems, suggesting a lack of a systematic and in-depth understanding of the characteristics and functions of the interrelated subsystems. Findings highlight the need to enhance teachers' metalinguistic knowledge of the English intonation system, with more emphasis on the interconnectivity of intonational features and contextual meaning-making phenomena of intonation. The study provides implications for second language (L2) teacher educators and education programmes, suggesting that more attention should be given to teachers' use of metalanguage for explicit pronunciation instruction. In addition, more training opportunities are needed to foster a systematic and in-depth understanding of the intonation system.