This book summarizes attachment processes across the lifespan and reviews clinical applications with infants, children, adolescents, and adults. Attachment theory is often mischaracterized as focusing solely on maternal influences in early childhood, but developmental science has explored the important roles that other attachment figures play throughout one's life, including foster parents, social peers, and romantic partners. Following the history and evolution of attachment research, this book translates foundational knowledge into clinical practice by reviewing interventions such as parent training techniques, attachment‑based family therapy, and mentalization‑based therapy. These attachment-based interventions are differentiated from other, harmful treatments that have been erroneously linked to attachment theory, being labeled by their proponents as “attachment therapy. Key concepts such as internal working models and secure vs. insecure attachment scripts are described, as are important assessment measures like the strange situation procedure and the adult attachment interview. Special features highlight notable topics and controversies in attachment theory and research and present case studies that bring clinical guidance to life.