PROJECT SUMMARY Worry and distress in cancer survivors are common, do not correlate with disease severity, and are heightened in young adults who are going through multiple life transitions related to school, work, relationships, and family. Moreover, prior studies found that cancer-related worry and distress can plague young adults many years after initial diagnosis and treatment, sometimes persisting for over 20 years. Thyroid cancer, melanoma, and testicular cancer represent the 2nd, 3rd, and 4th most common cancer types diagnosed in young adults, respectively. In addition to being common cancers in young adults, these three cancers share many other similarities, including accompanying unmet psychosocial needs. Key to managing worry and distress is ensuring individuals have knowledge about and confidence in their ability to engage in self-management of cancer-specific worry. The widespread use of mobile devices across diverse groups in the United States, as well as the promise of mobile health technology for reducing cancer disparities, supports the use of the mobile optimized Personalized Cancer Support for Young Adults (PerCS-YA) tool to reduce worry and distress while ensuring broad access by young adults from diverse socioeconomic and geographic backgrounds. Guided by the ORBIT model for the development of behavioral trials, we will conduct stakeholder-engaged refinement of the proposed intervention followed by a phase II efficacy trial utilizing a population-based recruitment source (Surveillance, Epidemiology, and End Results (SEER) – Georgia) as well as an online cancer support community recruitment source. Optimization will be followed by a process evaluation, in preparation for the future large randomized controlled trial (RCT). By tailoring to the young adult cancer population, incorporating mobile technology (i.e., PerCS-YA will be usable across mobile platforms such as iPhone and Android), and offering ongoing interactive support, there is potential to mitigate young adult cancer survivors’ worry and distress. Ultimately, this proposed targeted intervention will reduce the burden of cancer for young adult survivors.