The practice of securing informed consent from research participants has a relatively low profile in second language (L2) acquisition research, despite its prominence in the biomedical and social sciences. This review article analyses the role that informed consent now typically plays in L2 research; discusses an example of an L2 study where complex issues of informed consent surfaced; and summarizes debates about informed consent that are underway in other disciplines, but which so far have been little recognized in scholarship on L2 acquisition.