The book presents the methodology and techniques of mentalization-based group therapy (MBT-G) using examples from group leadership, group structure, and group composition in practice, in clinics, and day clinics. It describes the concept of the mentalization model in groups and clinically applied group psychotherapies. The neurobiological and developmental psychological prerequisites for language, speaking, and mentalizing in groups are discussed in detail. The methodology and techniques of MBT-G are illustrated through examples of group leadership, group structure, and group composition in practice, clinics, and day clinics, highlighting both the similarities and differences between MBT-G and traditional psychodynamic group psychotherapies for specific patient groups. Clinical vignettes are used to clarify the concept of mentalization.