Problem-based learning (PBL) is an innovative approach to language learning. Its effectiveness has been the subject of empirical studies in English as a foreign language and second language contexts such as Malaysia, Taiwan, Singapore, Pakistan, Iran, and Nigeria. Although the results have been promising, research in this area is still very scant. This paper examines studies that have been done on PBL with the aim of ascertaining what has been achieved and what areas warrant further research. The researchers conducted an online search using scientific databases to identify studies that had dealt with problem-based language learning. They found that most studies focused on the effect of PBL on the productive skills of speaking and writing, and were conducted mainly using quantitative and experimental approaches. They suggested that more studies could be done using qualitative approaches that examined the processes involved, as well as studies on PBL assessment.