Following the growth in visibility of Transgender and Gender Non-Confirming-identified people (TGNC) in popular culture and media, along with the increase in number of health clinics focusing on working with this population, and the development of a special interest in health professionals in TGNC-related issues, flourishing scientific literature and updated guidelines to help Mental Health Professionals (MHPs) work affirmatively with transgender individuals is pertinent. Despite the increased attention toward TGNC individuals, this population is still faced with political, economic, legal, and medical obstacles affecting their mental health and access to health care. Moreover, MHPs still report having limited training and experience in TGNC-affirmative care. This article aims at providing professionals with the most updated information and research findings to help them develop a more trans-affirmative practice. After defining key terms and providing a definition of TGNC-affirmative health care, this article will focus on summarizing the main documents that inform MHPs working with this population. This article offers research-based guidelines and discusses the major theoretical frameworks professionals are encouraged to incorporate in their work when developing TGNC-affirmative care. Additionally, this article will present the current debate around the diagnoses of Gender Dysphoria (DSM-V) and Gender Incongruence (ICD-11). The controversy between the Medical Model based on the Diagnosis of Gender Dysphoria and the emerging Informed Consent Model will be reviewed.