Mycoplasma genitalium is an important pathogen of acute non-gonococcal urethritis (NGU) in men and plays a significant role in persistent or recurrent NGU. In the management of patients with M. genitalium-positive NGU, eradication of the mycoplasma from the urethra is necessary to prevent persistent or recurrent NGU. Therefore, M. genitalium should be considered for antimicrobial chemotherapy of NGU. This article reviews the in vitro antimicrobial activities of antibiotics against M. genitalium and the efficacies of various antibiotic regimens against M. genitalium-positive NGU, including the doxycycline and azithromycin regimens recommended as first-line treatments for NGU in the guidelines. Selection of macrolide-resistant M. genitalium by treatment with the single-dose regimen of 1-g azithromycin and mechanisms of macrolide resistance in M. genitalium are discussed. The effectiveness of the moxifloxacin regimen against persistent or recurrent NGU, unsuccessfully treated with azithromycin and/or doxycycline regimens, is emphasized.