One in 68 Americans has autism spectrum disorder (ASD), and diagnosis is often delayed into adulthood in individuals without comorbid intellectual disability. Many undiagnosed adults resort to self-diagnosis. The purpose of this descriptive phenomenology was to explore the experience of realizing a self-diagnosis of ASD among 37 individuals who were not formally diagnosed. Results revealed five themes: feeling “othered,” managing self doubt, sense of belonging, understanding myself, and questioning the need for formal diagnosis. Healthcare professionals must have an understanding of self-diagnosis to help individuals transition to formal diagnosis and to adequately educate, support, and screen this population for comorbidities.