Mobile phones are becoming more acceptable toolkits to learn languages. One aspect of English language which has been subject to investigation in mobile-assisted language learning (MALL) is vocabulary. This study reviewed some of the studies conducted in various contexts on the effect of MALL on vocabulary learning. We investigated some of the most prominent databases such as Science Direct, Wiley, Scopus and Oxford to find these studies; believing that this study can have pedagogical implications for future researchers and language teachers. We attempted to select studies from different contexts, i.e., Malaysia, Taiwan, Korea, China, Japan, Iran, Saudi Arabia, Turkey, etc. Thirty studies were selected purposively in this way. Some of the main features of these studies are elaborated on in the discussion section. Pedagogical implications are discussed.