Engro Fertilizers successfully commissioned world largest single train Ammonia-Urea complex located in Daharki (Pakistan) at the end of 2010, capable of producing 3,835 MTPD Urea. This paper shares key learnings from some of the challenges faced and remedial measures taken for sustainable & reliable Urea plant operation. This paper shares Engro’s experience of operating world largest single train Ammonia-Urea complex which was commissioned successfully at the end of Dec 2010, with a capacity of 3835 Met/day prilled Urea. Due to swear gas crises in country, the complex has to undergo numerous start-up & shutdowns during the course of past 03 years. Since the commissioning of Urea plant, problems were faced in numerous forms and both short term & long term strategies were developed after carrying out meticulous root cause analysis in shortest possible span to keep the plant in operation. The paper highlights key learning’s from the issues encountered at Urea plant.