Aggregatibacter aphrophilus (Haemophilus aphrophilus) rarely causes endocarditis, endophtalmitis, osteoarthritis in human and is isolated from abscess materials. It is a member of oropharyngeal flora and dental biofilms. In this case, A. aphrophilus was isolated from a patient who had been operated due to acute appendicitis following dental surgery. Both conventional tests such as positivity of satellite phenomenon, X (hemin) and V(NAD) factor requirement and CO₂ requirement for growth, length of time to grow, and for further identification MALDI-TOF MS was used. After operation, the patient was treated with ceftriaxone and metronidazole and got total cure from the disease. Although it is a rare cause of disease in human, it should be kept in mind that Aggregatibacter species can cause disease in patients and should be differentiated from Haemophilus species.