In 2020, an estimated 1 in 4 non-Hispanic Black women in the U.S. experienced mental illness in the past year. Anxiety and mood disorders are the most common mental health conditions among Black women. Many interventions using mobile apps to deliver mental health interventions to reduce anxiety or depressive symptoms revealed that participants experienced a significant reduction of symptoms post-intervention; indicating that mobile apps are a promising tool for self-management. However, most of the studies conducted have no to low representation of Black women, which may affect the generalizability of the effectiveness for this group. While there are commercially available apps that are geared toward women of color, the majority lack scientific evidence to support their effectiveness. WellSis is a mobile app co-designed with Black women to support self-management of anxiety and depression. The current prototype has educational, self-tracking, and personal development features. We currently have funding to conduct consensus and co-design workshops with Black women (ages 25-34 years) with elevated anxiety or depression and licensed mental health professionals to create the therapeutic components of the WellSis app in Summer 2023. Our goal is to secure funding to support the development work of the culturally responsive Mindfulness-Based Cognitive Therapy features.