Roughly 30 years ago researchers in the second language acquisition (SLA) field started to take a focused interest in the study of inner speech (IS) and private speech (PS) processes in second language (L2) learning and use. The purpose of this review is to assess the status of current research and the progress made during the last ten years on the development and experience of covertly using a language other than the first. The review begins with a critical discussion of the challenges involved in defining and conceptualizing IS and PS. To conduct the search of relevant sources, a broad understanding of IS as "silent speech for oneself" and PS as "externalized speech for oneself" was adopted. After a brief synopsis of past research on L2 IS and PS, recent (2005-2015) work is discussed both from a generic-language stance and an L2, bilingual, and multilingual perspective. The review then takes a critical look at the difficult methodological issue of data collection on IS and PS, highlighting strengths and limitations in recent research. Pedagogical implications derived from the research reviewed and suggestions for future studies are discussed.