Immigration is a crisis-prone, complex process, often involving the need to acquire a new language, frequently at the expense of the mother tongue. Thus, the phenomenon of immigrants requiring various forms of mental health assistance while having limited fluency in the therapist’s language is widespread. Cognitive behavioral therapy (CBT) has become a widely prevalent therapeutic approach in many countries, including countries absorbing immigrants. This article reviews case studies that relate to the use of CBT with immigrants, both in individual and group sessions, focusing on the position of the patient’s mother tongue in the process. Research has persistently shown that the mother tongue is emotionally significant—using it, being exposed to it, expressing emotions and understanding emotions expressed in it, having access to it and to memories encoded in it, and the like. Given these dimensions, it plays a potentially important role in the therapeutic process. The pivotal question, then, is whether a therapeutic process that is essentially emotional can be effective if the mother tongue is not an inherent part of it. This article addresses this issue while examining the mother tongue’s position in CBT, the therapists’ awareness of these issues, the accommodations, if any, made in this regard, the therapists’ point of view, and suggestions for improving the use of CBT with immigrants. It is written to be of relevance to a diverse audience including researchers from varied disciplinary backgrounds, therapists who work with multilingual patients (especially immigrants or members of other minority groups) or are multilingual themselves. Our aims, therefore, are to contribute to the theoretical understanding of the mother tongue’s centrality in emotional processes and to offer some practical recommendations for therapists and training institutions.