Cancer is the second most serious health problem and the second leading cause of death in human. The cancer patient undergoing treatment experiences Physical and Psychological problem. The physical problems, like hair loss, nausea and vomiting and initial diagnostic phase can be very stressful. The cancer patient undergoing treatment experiences a psychological distress including anger, anxiety, sadness, fear, stress, feeling out of control, feelings of depression, impairment of concentration, sleep disorders, mental and cognitive reservation and psychiatric disorders. In India the cancer patient undergoing treatment were having the depressive disorders 4.5%, anxiety disorders 3%, stress disorder 4% in total population. Progressive Muscle Relaxation Technique is help to reduce the stress, anxiety and depression among cancer patient to promote general wellbeing. A study to assess the Effectiveness of Progressive Muscle Relaxation Technique on Stress, Anxiety and Depression among Patients undergoing Cancer Treatment in Puducherry Cancer Trust Hospital and Research Centre at Puducherry. The Research design chosen for this study was Quasi – Experimental Design (One group pre-test and post-test design). The study conducted in selected Hospital at Puducherry. The population includes the patient undergoing cancer treatment are taken as population and out of that 60 patients were selected for this study. The sampling technique used for this study is Simple Random Sampling technique (Lottery method). The Frequency and Percentage distribution are used to assess the Pre-test and Post-test level of stress, anxiety and depression among patients, Wilcoxon Signed Ranks test are used to evaluate the Effectiveness of Progressive Muscle Relaxation Technique on level of Stress, Anxiety and Depression among patients and Chi-square test to associate the level of Stress, Anxiety and Depression with the selected demographic variables of Patient Undergoing Cancer treatment.