Myiasis in humans is a disease caused by larvae of various fly families. It mainly occurs in communities with poor sanitation and low socioeconomic status. Meanwhile intrahospital or nosocomial myiasis represents a rare phenomenon but is of relevance to public health. Here, we report an outbreak of myiasis caused by Cochliomyia macellaria in five patients hospitalized for several diseases at the Service of Internal Medicine of the Hospital Regional Universitario de Colima, Mexico during June and July 2021. Three patients were males and two were females, aged 37 to 83 years. All were affected by myiasis caused by larvae of the fly C. macellaria. Three patients underwent invasive mechanical ventilation; one had cutaneous basal cell cancer and one had advanced diabetic foot. This event occurred after 4 days of hospitalization and in the same hospital pavilion. Two patients died, and the others were discharged after treatment with antibiotics and ivermectin. We believe that this nosocomial cluster represents a more frequent phenomenon than reported in tropical countries, where authorities should pay attention to its timely detection, especially in vulnerable populations.