This book discusses the concepts of emotional regulation and dysregulation. It focuses particularly on exploring some of the theoretical elaborations on which these terms have been based, their meeting point with the transdiagnostic approach and their relevance for mental health. In addition, two instruments are presented that are the product of the efforts of different authors in the quest to further develop this field of research. The two instruments discussed are the Cognitive Emotional Regulation Questionnaire (CERQ) and the Difficulties in Emotional Regulation Scale (DERS). Finally, some criticisms and issues to be explored regarding the concepts of emotional regulation and dysregulation in the field of clinical psychology are detailed.