Human immunodeficiency virus (HIV) infection can weaken the immune system causing its inability to combat opportunistic infections. Managing the complexity of these opportunistic infections has created a challenge for healthcare professionals. Our knowledge on the aetiological agents causing opportunistic infections in immunocompromised hosts has increased over the last decade. Diarrhoeal diseases are frequent complications associated with HIV-infected patients. For most of the causes of diarrhoea, the clinical signs are non-specific, and the laboratory diagnostic workup is neither easy nor fast. This review provides data on aetiological approaches of common diarrhoeal diseases including viral, microbacterial, parasitic, bacterial and fungal infections, and HIV enteropathy; diagnostic evaluation; and treatment of diarrhoea in HIV-infected patients. This article will be helpful for those who are in the practice of managing diarrhoea in such patients.