Constipation is a frequent, distressing, and underestimated complication in patients with advanced cancer. It may develop from general disturbances that may or may not be cancer related, but the use of opioids is one of the main causes in this population. Opioids affect the intestine by reducing motility and secretions and by increasing fluid absorption and blood flow. Untreated constipation may lead to several complications. Effective management of constipation starts with a careful assessment of the patient, including the history of the frequency and difficulty of defaecation, symptoms caused by constipation, and physical and rectal examinations. When the diagnosis of constipation is unclear, an abdominal X-ray may be required. The treatment of constipation includes general interventions, such as the availability of comfort and privacy or the elimination of medical factors that may contribute to constipation, and therapeutic interventions including oral or rectal laxatives and the use of prokinetic drugs and naloxone. The purpose of this paper is to review the pathophysiology and causes of constipation and the effects of opioids on the gastrointestinal tract, and to propose an approach for its assessment and management. Randomized clinical trials between different laxatives and/or prokinetic agents in cancer patients are needed, and future studies should focus on the validation of different clinical assessment tools for constipation.