Synovial sarcoma accounts for 5-14% of all soft tissue tumours. We present a case of 35 year-old male who presented with five months history of progressively increasing shortness of breath and cough. On evaluation, there was no air entry on the left side. CAT scan chest showed a large necrotic mass involving the entire left hemi-thorax. The tru-cut biopsy of this mass was done and it showed synovial sarcoma. The entire tumour along with the lung and the pericardium was removed completely. The Patient had an uneventful recovery and was discharged home in 10 days with follow-up for adjuvant chemotherapy. Due to the rarity of this disease, no guidelines for the treatment are available. Main existing treatment includes surgery followed by either radiation, chemotherapy or both. Synovial sarcoma should be considered in the differentials of an adolescent or adult male Patient presenting with a mass in the thorax.