Psoas abscesses account for 5-10% of abdominal suppurations. They can be primary or secondary. Primary polymicrobic abscesses of the psoas muscle including, in particular, tuberculous abscesses and pyogenic abscesses, have never been reported in the literature. We report the case of a 35-year old patient, with no particular past medical history, admitted with pain in the right lumbar fossa associated with a fever of 40°C. Onset of symptoms had occurred 5 months before, but without fever. Abdominal CT scan showed an abscess of the right external transverse and oblique psoas muscles extended to the retroperitoneum and infiltrating the thoracoabdominal wall. Cytobacteriological examination of pus showed fast-growth monomorphic wild-type Escherichia coli strains. Systematically performed Real-time PCR test for the detection of Complex Mycobaterium tuberculosis was positive while direct examination after Ziehl-nelseen staining was negative. The culture on a solid Lowenstein Jensen medium was positive after one-month of incubation. The outcome of our patient was favorable under antibacillar quadritherapy and ceftriaxone. This study highlights that a tuberculous origin should be systematically suspected in patients living in endemic areas with chronic, recurrent psoas abscess not responding to antibiotics.