Understanding Parental Alienation offers a clear, accessible starting point for anyone trying to make sense of parental alienation (PA): what it is, how it develops, and why it causes such profound harm. Opening with a grounded, user-friendly explanation of the phenomenon, the book demystifies PA without minimising its seriousness, setting the stage for a deeper exploration of its emotional, psychological, and legal dimensions. From there, the book moves into a comprehensive examination of why parental alienation happens. Drawing on attachment theory to family-violence frameworks, it brings together leading theoretical insights to illuminate the mechanisms that drive bond-breaking between parents and children. This book expands beyond previous work to examine the wider ecosystem around PA, including the role of new partners, extended family members, complex sibling dynamics, and the systems that enable the abuse to take place. The book then shifts to impact: analysing the short- and long-term consequences for every actor involved – children, targeted parents, alienating parents, siblings, and professionals encountering PA in practice. Finally, the book offers extensive practical guidance. It equips parents, practitioners, and policymakers with concrete, research-rooted strategies for recognising alienating behaviours and responding effectively. Alongside general principles for prevention and intervention, it includes tailored advice not only for affected parents but also for children and young people living through these dynamics. Accessible, yet academically robust, Understanding Parental Alienation is a multi-purpose guide for mental health professionals, legal practitioners, family-court personnel, and families navigating post-separation conflict. It delivers the foundational knowledge and practical tools needed to understand this complex issue and to begin changing it.