Background Despite a great deal of studies on blended language learning, synthesized empirical evidence of its effects on language performance is still lacking. Objectives To bridge the gap, this study aimed to meta‐analyse the effects of blended language learning on EFL learners' language performance. Methods Drawing on the framework of AT (Activity Theory), this paper reported results based on a meta‐analysis of the effects of blended language learning on EFL (English‐as‐a‐foreign‐language) learners' language performance with 43 valid effect sizes from 39 experimental and quasi‐experimental studies published during 2000–2021. Results and Conclusions The results showed that the overall effect size was significantly moderate for language performance, suggesting that blended language learning is more effective than traditional methods. The moderating effects of AT‐related moderators were analysed. The educational levels, intervention durations, geographic regions and software types were found to be significant moderators, while others did not find a significant moderating effect. Implications The results also provided some practical insights into the pedagogical implications for teachers, practitioners, and researchers in blended language learning. Lay Description What is already known about this topic The facilitative effects and educational affordances of blended language learning have been well‐documented. Existing studies have been helpful in affording insights into the use of blended language learning. It is difficult to understand the effect size and potential moderators of blended language learning. What this paper adds Few studies to date published have directly and systematically meta‐analyse the use of blended language learning. This study meta‐analyzes literature on blended language learning with respect to the framework of activity theory. Blended language learning is found to be more effective than traditional methods. Implications for practice Pedagogical potentials of blended language learning should be encouraged to explore among EFL learners of different educational levels. Educational affordances of blended language learning should be integrated into the curriculums depending on the educational needs and purposes. Researchers should design the research with larger sample sizes and long‐term durations to increase the reliability of findings.