The aim of this randomized controlled trial was to evaluate the effectiveness of the EMDR-Integrative Group Treatment Protocol for Ongoing Traumatic Stress (EMDR-IGTP-OTS) in reducing posttraumatic stress disorder symptoms, depression and anxiety symptoms related to the diagnosis and treatment of cancer. Twenty-three adolescents and young adults (13 male and 10 female) with different types of cancer (breast, leukemia, lymphoma) and PTSD symptoms related to their diagnosis and cancer treatment met the inclusion criteria. Participants age ranged from 13 to 22 years old (M = 16.71 years). Participant's time since diagnosis varied from 2006 to 2018. Participants in treatment (N=11) and no-treatment control (N=12) groups completed pre, post, and follow up measurements using the Posttraumatic Stress Disorder Checklist for DSM-5 (PCL-5) and the Hospital Anxiety and Depression Scale (HADS). Data analysis by repeated measures ANOVA showed that the EMDR-IGTP-OTS was effective in significantly reducing symptoms of PTSD, anxiety, and depression, with symptoms maintained at 90-day follow-up and with large effect sizes (e.g., d=1.17). A comparison of the treatment and no-treatment control groups showed significantly greater decreases for the treatment group on symptoms of PTSD, anxiety, and depression. This study suggests that EMDR-IGTP-OTS may be an efficient and effective way to address cancer-related PTSD, depressive, and anxious symptoms in adolescents and young adults.