Due to their experience of managing two languages, it has been suggested that bilinguals could receive more practice in the domain of working memory (WM) leading to a WM bilingual advantage. Although some studies have shown that bilinguals can outperform monolinguals in WM tasks, the studies investigating WM capacity in bilinguals provide inconsistent findings regarding the existence of a bilingual advantage. We therefore conducted a meta-analysis on the association between bilingualism and WM capacity. Data from 116 studies (involving 177 pairs of participants and 444 effect sizes) were extracted. Based on previous findings, we examined age, characteristics of the WM tasks--i.e. complexity (simple span vs transformation vs complex span tasks) and domain (verbal vs nonverbal)--age of first exposure to L2, and L2 proficiency as potential moderating variables. Results indicated a small bilingual advantage in WM (g = 0.12, p = 0.054), which was moderated by the language used in the verbal WM task. The bilingual advantage was stronger when the verbal WM task was performed in L2 compared to L1. Thus, the bilingual experience is associated with slightly higher WM capacity. Nevertheless, future studies would benefit from greater consideration of individual differences within groups of bilingual individuals.