Spontaneous abscess of the corpus cavernosum is an extremely rare presentation. This is the first documented case of corpus cavernosal abscess caused exclusively by organisms from the Streptococcus milleri group, which have previously been described as being associated with abscess formation. This report outlines the case of a 56-year-old alcoholic male with no risk factors who presented with an 8-day history of penile pain, swelling and sepsis. A diagnosis of abscess of the right corpus cavernosum was confirmed by magnetic resonance imaging. Management required intravenous antibiotics, penile exploration, incision and drainage. Streptococcus constellatus and Streptococcus intermedius were isolated. The aetiology, diagnosis, management and microbiology of this unusual presentation are discussed, and the few previously documented cases of abscess of the corpus cavernosum are reviewed.