Chronic diarrhea is a common reason for consultation in renal transplant patients. Cytomegalovirus infection is the cause of chronic diarrhea of infectious origin in 50% of cases, but coinfection with tuberculosis is rare. We present the case of a renal transplant patient with chronic diarrhea, with a finding of left colon colitis and positive microbiological studies in biopsy for tuberculosis and cytomegalovirus. The patient received valganciclovir and anti-tubercular treatment with adequate evolution. Immunosuppressed patients may have diarrhea secondary to opportunistic infections; therefore, an algorithm for early diagnosis and treatment is recommended.