EMDR therapy administered to patients with cancer has proven to be effective in the reduction of posttraumatic stress disorder (PTSD) symptoms and PTSD diagnosis remission. The main objective of this study was to measure the PTSD scores and diagnosis changes before and after the provision of the EMDR-Protocol for Recent Critical Incidents and Ongoing Traumatic Stress (EMDR-PRECI) to female patients with cancer-related PTSD diagnosis. A secondary objective was to observe the immunoglobulins and the cortisol changes pre and post-treatment. Seven female patients with different types of cancer (5 breast, 1 colon, and 1 lymphatic cancer), different cancer treatments (radiation, chemotherapy, radiation, and chemotherapy), and PTSD diagnosis related to their diagnosis and cancer treatment met the inclusion criteria. Participants' age ranged from 40 to 57 years old (M = 52.28 years old). For PTSD diagnosis and total scores, we used the Global Assessment of Posttraumatic Stress Questionnaire validated for the Mexican population. Biomarkers (cortisol and immunoglobulins) were measured before and after EMDR treatment. For the neuroendocrine measure, we used the cortisol levels in the participant's blood. For the immunological measure, we used the Nephelometry technique. We measured the changes in the following types of antibodies (immunoglobulins): a) Immunoglobulin A (IgA), b) Immunoglobulin G (IgG), and c) Immunoglobulin M (IgM). EMDR-PRECI was provided by three licensed EMDR clinicians formally trained in the protocol administration. Each EMDR-PRECI session lasted 50-60 minutes. The minimum number of sessions was three and the maximum ten with an average of five. Treatment focused only on the distressing memories related to diagnosis and cancer treatment. No adverse effects were reported during treatment or at six months post-treatment assessment. Results showed a full PTSD diagnosis remission in all participants with significant differences for PTSD scores, t (6) = 2.44, p < .05. These results are in concordance with Carletto et al., study in which all patients treated with EMDR no longer met criteria for PTSD [12]. No significant differences were found for immunoglobulins or cortisol. We believe that the administration of the EMDR-PRECI could be an efficient and effective component of a psychosocial approach to reduce or eliminate cancer-related PTSD symptoms and diagnosis.