We assessed the relationship between infection with Mycoplasma genitalium, an emerging sexually transmitted pathogen, and cervical shedding of human immunodeficiency virus (HIV)-1 DNA among 303 HIV-1-positive Kenyan women. HIV-1 shedding was detected by qualitative polymerase chain reaction (PCR) in 154 women (51%); M. genitalium was detected by qualitative PCR in 52 (17%), and organism burden was determined by quantitative PCR. Women with high M. genitalium organism burdens (more than the median of 3195 genomes/mL) were 3-fold more likely to shed HIV-1 DNA than were M. genitalium-negative women (adjusted OR, 2.9 [95% confidence interval, 1.1-7.6]), yet this did not appear to be mediated by traditional measures of cervical inflammation (elevated polymorphonuclear leukocyte count).