Mycoplasma hominis infections outside the urogenital tract are uncommon. An unusual case of sternal infection caused by both Mycoplasma hominis and Ureaplasma urealyticum is described. This is the first report found in the literature of mixed infection due to these microorganisms at this site. The outcome was favourable after drainage of the surgical wound and antibiotic therapy with clindamycin, gentamicin and doxycycline.