The suffering of patients with incurable cancer is determined to a large degree by the presence and intensity of the symptoms of their disease. Knowledge of symptom prevalence is important for clinical practice. The main aim of this study was to obtain a reliable estimation of symptom prevalence in patients with incurable cancer by performing a systematic review of studies assessing this topic. We included 44 studies (including 25,074 patients) on overall symptom prevalence (Group 1) and six studies (including 2,219 patients) on symptom prevalence during the last one to two weeks of life (Group 2). In these studies, symptom prevalence was assessed by a questionnaire, a standardized interview, or the medical record. We identified 37 symptoms assessed in at least five studies. Almost all symptoms occurred in more than 10% of the patients. Five symptoms (fatigue, pain, lack of energy, weakness, and appetite loss) occurred in more than 50% of the patients of Group 1. Weight loss occurred significantly more often in Group 2 compared to Group 1, and pain, nausea, and urinary symptoms occurred significantly less often. Generally, symptom prevalence was highest if assessed by a questionnaire. The results of this study should be used to guide doctors and nurses in symptom management. Proper attention to symptom burden and suffering should be the basis for individually tailored treatment aimed at improving or maintaining quality of life of patients in their last period of life.