We present a case of pleural tuberculosis (TB) in a patient on infliximab for ankylosing spondylitis. A 36-year-old male presented to our hospital with low back ache of inflammatory type along with multiple symmetric inflammatory type of joint pain. Further clinical examination, laboratory and radiological investigations were suggestive of ankylosing spondylitis. He was initially treated with nonsteroidal anti-inflammatory drugs but citing poor response it was decided to initiate biologic therapy using infliximab (antitumor necrosis factor-alpha). Mantoux test and chest radiograph were done before the therapy to rule out TB. Following three doses of infliximab, patient came with complaints of fever and cough for 1 week. On investigation, it was found to be a case of pulmonary TB. This shows the importance of close monitoring of patient for TB among patients on infliximab even though the screening test has come out to be negative.