Obsessive-Compulsive Disorder (OCD) is a debilitating mental illness affecting many people globally. Currently the most successful treatment is Cognitive Behavioural Therapy (CBT), which can improve the symptoms of 75% of patients (OCD UK 2020). Journaling is an essential part of CBT because it allows patients to track their thought patterns and make connections between their thoughts and their behaviours. However, this often relies on patients recording this information in a physical journal, which can be inconvenient in many ways. While there are existing applications available for CBT journaling, none of them are designed specifically for OCD and they lack features such as being able to share entries with therapists. This project therefore looks at this problem in a new way and aimsto create a thought journal mobile application that assists patients and therapists in the process of treating OCD through CBT.