Anti-tumor necrosis factor-α (TNF-α) is a principal treatment for Crohn's disease (CD). However, it increases the susceptibility to tuberculosis (TB) infection, and therefore, screening examination prior to treatment initiation is crucial. Here, we report the case of a patient with CD who developed pulmonary TB following anti-TNF-α therapy, despite negative screening. A 19-year-old female who had no history of TB or had traveled to TB-endemic regions was diagnosed with CD. After negative TB screening with chest X-ray and interferon-gamma release assay, the patient was initiated on oral prednisolone and pH-dependent mesalazine. The treatment was changed to infliximab (IFX) because of the inadequate response observed to prednisolone;however, she developed pulmonary TB only 10 weeks after the initiation of IFX. The standard short-course anti-TB regimen was initiated to treat pulmonary TB, whereas IFX was discontinued and replaced with budesonide. Our case suggests that the risk of developing TB should not be excluded, despite the initial negative TB screening, particularly when a patient develops respiratory symptoms during anti-TNF-α therapy.