Moellerella wisconsensis is a Gram-negative, facultative anaerobe bacillus in Enterobacteriaceae, and it is an uncommon pathogen in domestic animals. To date, a total of 5 cases were reported including 2 dogs, 2 cattle, and a goat. Streptococcus equisimilis is the second common bacterial agent after the S. equi subsp. zooepidemicus in equine pneumonia cases. The present report describes the isolation of M. wisconses in lungs and spleen in a 10-year-old Arabian horse at post mortem examination that is co-infected by Streptoccus equisimilis. Clinical and pathological findings included bilateral nasal discharge, conjunctivitis, sternal recumbency, severe diffuse necrosuppurative rhinitis, multifocal fibrinopurulent pneumonia and purulent lymphadenitis. PCR assys showed no viral nucleic acids of EHV-1, EHV-4, EAV, EPV. The antibiogram testing revealed the isolate was sensitive to many antibiotics except for colistin. Taken together, the present report documents the first isolation of Moelerella wisconsensis in lungs and spleen in the horse, hence, experimental studies are needed to clarify for the pathogenity and pathogenesis of Moelerella wisconsensis.