A 24 years old primigravida underwent a routine ultrasound scan at 26 weeks of gestation; which showed a single normal growing foetus with intrathoracic mass on the left side of thoracic cage along with left displacement of cardiac apex. The mass was closely associated with lower portion of left lung. The extralobar sequestration was diagnosed which was further confirmed by colour Doppler during foetal period and by computed tomography and x-ray chest postnatally. Surgical excision was done.