This current and comprehensive handbook will guide educators, students, and clinicians in developing the awareness, knowledge, and skills necessary to work effectively with LGBTQI+ populations. Twenty-five chapters written by experts in the field provide direction for working with clients in an authentic, ethical, and affirmative manner that is tailored to their individual strengths, needs, and identity. The book is divided into four sections, which explore the science behind gender and affectional orientation; developmental issues across the life span and treatment issues; the specialized needs of nine distinct populations; and the intersectionality of ethnicity and overlapping identities, the role of religion, and counselor advocacy. To further a deeper understanding of the content, each chapter contains an “Awareness of Attitudes and Beliefs Self-Check,” a case narrative relating to the material covered, questions for discussion, and a list of online resources. The book concludes with an extensive glossary of terms, both preferred and problematic, which counselors working with these communities should understand and use appropriately.