The lives of lesbian, gay, bi-, pan-, asexual, and transgender (LGBTA+/LGBT) people are not considered to be standard in society, unlike those of heterosexual cisgender people. This can lead to prejudices against LGBT people and may negatively influence their access to high-quality health care. Medical and mental health care have been characterized by attitudes (psycho-)pathologizing LGBT lives and therefore supported the stigmatization of LGBT people in the service of heteronormativity. Mental health professionals (MHPs) largely have transferred principles guiding counseling and psychotherapy with heterosexual (straight) cisgender persons to treatment of LGBT individuals without considering the specific features of LGBT lives. This is true even if the treatment is not exclusively LGBT-related, but can address LGBT-unrelated issues. To counteract this, the present paper aims to provide an insight into ethically sound mental health care for LGBT people. By applying the principles of biomedical ethics, we have analyzed how LGBT individuals can be discriminated against in mental health care and what MHPs may need to offer LGBT-sensitive high-quality mental health care. We argue that MHPs need LGBT-related expertise as well as LGBT-related sensitivity. MHPs should acquire specialist knowledge for the diverse lives and the challenges of LGBT people. We encourage MHPs to develop an understanding of how their own implicit attitudes towards LGBT people can affect treatment. However, the demand for special training should not be mistaken as a demand for a specific type of mental health care. The principles of general psychotherapy are equally the basis of psychotherapy with LGBT people.