Tuberculosis (TB) has always been a burden in developing nations like India. Both pulmonary and extrapulmonary manifestations of TB have been seen widely in the pediatric age group with the specific age-wise distribution. We hereby report a case of a 15-month-old male child who was brought with complaints of localized pain in the left knee and was initially diagnosed to have juvenile-onset oligoarthritis. As the symptoms progressed and a cystic swelling was observed in the left popliteal fossa, he was investigated and aspiration of the cyst was done. Mantoux test done in the child was strongly positive and pus aspirated from the cyst was positive on cartridge-based nucleic acid amplification testing (CBNAAT) for Mycobacterium tuberculosis with rifampicin sensitivity. He was promptly started on 4 drug anti-TB therapy. The pus grew acid-fast bacilli in a culture medium which confirmed the diagnosis. Very young age (15 months) of presentation with cystic lesion from a joint is an unusual presentation of tubercular arthritis.