Fluoroquinolones, which are widely used to treat community-acquired pneumonia, also have excellent in vitro activity against Mycobacterium tuberculosis. A retrospective cohort study was conducted among adults with culture-confirmed tuberculosis to assess the effect of empiric fluoroquinolone therapy on delays in the treatment of tuberculosis. Sixteen (48%) of 33 patients received fluoroquinolones for presumed bacterial pneumonia before tuberculosis was diagnosed and treated. There were no differences between the group who did and the group who did not receive fluoroquinolones, except that patients who received fluoroquinolones were more likely to present with shortness of breath. Among patients treated empirically with fluoroquinolones, the median time between presentation to the hospital and initiation of antituberculosis treatment was 21 days (interquartile range, 5-32 days); among those who were not, it was 5 days (interquartile range, 1-16 days; P=.04). Initial empiric therapy with a fluoroquinolone was associated with a delay in the initiation of appropriate antituberculosis treatment.