Psoas abscess is a pus collection within the muscle compartment. It is a very uncommon entity. It can be primary as a result of haematogenous spread or secondary as a consequence of a direct extension of an infectious focus. Diagnosis is usually delayed because nonspecific clinical presentation. Staphylococcus aureus is the most common organism cultured in this type of abscess. We describe a secondary psoas abscess in an elderly female patient. The patient presented with fever, right groin pain and malaise. Following laboratory, radiological and microbiological analyses the patient was diagnosed as having a psoas abscess due to Pasteurella multocida, which is a Gram negative bacteria, part of the normal oral flora of many animals and can causes human infections after animal scratches or bites. More rarely is to find this organism causing psoas abscesses. Because of insidious clinical presentation, the diagnosis of psoas abscess is a challenge and a high index of suspicion is required. We emphasize the importance of bacteriological confirmation of microorganism involved to choose the correct antibiotics. Percutaneous drainage is the treatment of choice. Open surgical drainage should be reserved if percutaneous drainage fails.