Diaphragmatic agenesis is the most extreme form of congenital diaphragmatic defect, and it may be unilateral or bilateral. Diaphragmatic agenesis is a rare diagnosis, typically made early in infancy and is generally associated with other genetic anomalies, especially aneuploidy syndromes. It is associated with a high mortality, if not treated in infancy. However, a few patients have survived till adulthood. In this report, we describe the case of an adult female who presented with progressive shortness of breath during the second trimester of pregnancy with agenesis of the left side of the diaphragm. Open diaphragmatic hernia repair done with dual mesh closure after which patient improved symptomatically and lung showed good expansion.