My paper offers a new interpretation of Mrs. Dalloway through proving that Septimus, a World War I army veteran, suffers from post-traumatic stress disorder (PTSD). Although this diagnosis did not exist at the time of the novel, through using the 2013 Diagnostic and Statistical Manual of Mental Disorders (DSM), the character can be granted an accurate diagnosis, aiding in understanding the character himself. I will be able to diagnose him due to symptoms such as: hallucinations, apathy, signs of depression, inability to cope, and eventual suicide. In addition to understanding, critical information about the audience will also be granted, such as answering whether or not the audience of 2016 is more empathetic towards Septimus than the audience of the 1920s, therefore changing how the entire novel is read and understood. In addition to the DSM, common attitudes towards what would have been known as “shell shock” will add more information about audience attitudes towards Septimus.