Purpose: Despite numerous studies reporting beneficial effects of metacognition for improving learning or developing self-regulated learners, the evidence from tertiary English as a Foreign Language (EFL) settings is still unclear as synthesis studies in this field remain rare. To address the gap, this study sought to identify, examine and synthesise relevant studies on the effectiveness of metacognitive interventions in tertiary EFL contexts. Design: The study adopted a systematic review approach to include all relevant studies that could be identified for analysis. Seven data sources were searched to identify studies which were, then, screened for relevance based on a pre-specified protocol. The included studies underwent data extraction and quality appraisal before data syntheses via a meta-analysis and a thematic synthesis. Findings: The results indicate the high potential of metacognitive interventions for EFL learners and the fundamental role of explicit instruction, clear pedagogical sequencing and the regulation of skills, rather than merely focusing on knowledge about metacognition, for the successful interventions. Moreover, limitations in the data quality suggest that more rigorous investigations are needed to provide a more overarching overview of the impact of metacognition-based studies in tertiary EFL contexts. Originality/Value: As synthesis studies on the topic are scarcely available in tertiary EFL contexts, this study can offer a more evident indication of the effectiveness of metacognitive instruction for EFL learners. From comprehensive and rigorous reviewing, it also proposes some practical guidelines and implications for further EFL policy and practices.