Pain is a subjective feeling, and there are no physical tools or instruments available to measure pain. Pain assessment in the clinical setting is a crucial step in the management of pain in inpatient as well as outpatients setting. Pain is accepted as a fifth vital sign in the healthcare setting, like other vital signs, pain can not be measured by any instrument because of a subjective nature as other vital signs are objective in nature. Adequate and accurate assessment and documentation, and thereupon management of pain ensures that each and every patient, from acute to chronic illnesses including terminal ill patients, hasbenefitted from efficacious pain-relieving measures. It has been estimated that 18 million people globally have cancer pain, and in that proportion, approximately 60% to 90% of the pain is caused by advanced tumors and 30% caused by mild and/or moderate tumors that can be treated by medical surgical or other therapy. Pain is classified as nociceptive and neuropathic based on the fundamental pathophysiology of pain. Assessment of pain can be done in three ways, Self-report, Behavioural how the patient behaves, and Physiological clinical observations. Conclusion: Pain is a worldwide health issue. Pain assessment & Management requires the attention of health professionals. Pain is one of the most common under evaluated vital signs in the health care sector. Under evaluation causes, discomfort to the patient as well as psychiatric problems, Better evaluation of pain stimulates good therapeutic management of it which improves the quality of life among patients pain assessment & management is complex, there are varieties of factors that affect pain assessment and management services thus a deeper understanding of the barriers and overcoming to this barrieris required for proper and effective pain management services.