This thoroughly revised edition uses an intersectional, social justice lens to teach practitioners how to competently and compassionately work with trans and nonbinary (TNB) clients and help them flourish. Research and clinical knowledge have been significantly updated to reflect emerging knowledge of gender diversity, including an expanded multicultural focus and the unique experiences of TNB people of color. New chapters debunk bad science on TNB people, discuss working with TNB clients in sports and other physical activities, and how to treat trauma and suicidality among TNB clients. The book addresses challenges that TNB individuals and communities face, including ongoing legal assaults on their rights and identities, while resolutely promoting joy and thriving through affirmative practice. Chapters translate scientific knowledge into practical guidelines for therapists in multiple areas, including interdisciplinary collaborative care with other helping professionals, such as physicians and social services, as well as social and legal advocacy. They also offer guidelines for working with TNB clients across different racial and ethnic identities; religious and spiritual beliefs; and developmental stages, from gender-questioning youth to older adults.