Autism spectrum disorder is diagnosed more in males than females, this difference is even more prevalent if the female is of at least average intelligence. The problem addressed by this qualitative exploratory case study was the under-identification of females with autism due to their masking behavior. This problem directly impacts females who obtain an autism spectrum disorder late in life and/or are misdiagnosed with a different disorder/disability. The purpose of this qualitative exploratory case study was to identify shared characteristics and behaviors among females with autism spectrum disorder who exhibit masking behavior. The guiding theoretical framework for this study was the Social Identity Theory, which states that all individuals are motivated by achieving and maintaining a positive self-concept. The researcher proposed that this motivation leads females with autism spectrum disorder to mask symptoms and behaviors that may be viewed negatively in society so that they can fit in. A qualitative exploratory case study was conducted in the state of Texas with a sample size of 38 total participants: twenty-eight females with autism spectrum disorder and ten parents of females with autism spectrum disorder. Data was collected using open-ended questionnaires created in Qualtrics. Links to the questionnaires, as well as the research study's problem, purpose, requirements, and contact information, were posted in Autism specific Facebook groups to solicit participants. The questionnaires revealed five themes: environmental influence, social masking behaviors, emotional masking behaviors, behavior traits, and effects of masking. The implications of the study revealed the need for timely diagnosis, proper training of diagnosticians and clinicians as it relates to social functioning, and the understanding of the role the environment plays in the behavior exhibited by females with autism spectrum disorder during the diagnostic process. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]