Mindfulness, as an ancient practice, has also started to be incorporated into second or foreign language settings in recent years. Due to this new and novel integration into the field, practitioners in foreign language teaching contexts are not clear about what mindfulness means and how it can be used in the classroom. This systematic review aims to present a general synthesis of studies conducted in English as a Second or Foreign Language (ESL/EFL) contexts in relation to mindfulness. For this purpose, various databases were searched and 23 relevant studies were included in the review. First, the most frequent themes explored in mindfulness studies were identified. Then, the main findings of the selected studies were analyzed under two categories, studies with intervention and studies without intervention. The findings revealed that the most frequently investigated themes in mindfulness studies are foreign language anxiety and language performance. The findings revealed that mindfulness treatments employed in the studies were found to have mostly positive effects on ESL/EFL learners. Furthermore, studies conducted without intervention pointed out a positive relationship between mindfulness skills and foreign language education. Overall, the findings of this review, pedagogical implications and further research are discussed in the paper.