This chapter reviews research on the development of sexual identity throughout the lifespan, with attention to older age. Sexual and gender identity are fluid. They do not remain the same throughout the life course. The internal feelings and external presentations of sexual identity and gender identity – known as congruence – are vital to understanding the person. With more individuals entering older age with non-heteronormative and non-binary sexual and gender identities, it is vital we pay close attention to their needs and wants. This chapter provides an overview of identity and identity formation, discusses identity formation in older age, and presents ways social workers can remain engaged, informed, and drivers of best-practices with our aging population.