Lesbian, gay, bisexual, transgender and queer or questioning psychology (LGBTQ psychology) is a branch of psychology that promotes inclusiveness in theory and practice across the science of psychology, affirming the lives of people with different sexual orientations and forms of gender expression in a non-heterosexist and non-genderist perspective. This article highlights the historical development of LGBTQ psychology in the context of different realities for LGBTQ people in five different countries (Russia, Greece, Colombia, South Africa and the province of Quebec, Canada). Key experts on LGBTQ concerns report distinctive challenges they have faced when promoting LGBTQ rights and developing LGBTQ psychology (e.g., the pathologization and criminalization of sexual diversity, neglect on the part of authorities, and rejection from religious groups). Human and mental health sciences have played an important role in the blossoming of LGBTQ psychology. Cross-cultural narratives show that the recognition of lesbian and gay rights comes before the recognition of the rights of bi, trans, queer and questioning people. Various forms of homonegativity and transphobia still coexist even in countries that have established protections and rights recognition for LGBTQ people. We provide 15 strategies to help psychological organizations and psychologists around the world promote the development of LGBTQ psychology.