The Grand River Conservation Authority (GRCA) has recently completed the fifth phase of a multi-phased rehabilitation program to extend the service life of the Conestogo Dam, a major water control structure in southwestern Ontario. Constructed in 1958, the dam plays an essential role in flood mitigation and low-flow augmentation within the Grand River watershed, while also supporting recreational use through a reservoir capacity of approximately 60 million cubic meters. This paper presents a case study of recent phases of the Conestogo Dam rehabilitation program and lessons learned during delivery. The upstream rehabilitation work completed in Phases 4 and 5 improved the reliability, safety, and service life of the dam by addressing deterioration of key structural components, including the wingwalls and piers. A phased approach was adopted to maintain dam operations and discharge capacity throughout construction, minimizing impacts to surrounding communities and the environment. The work included replacement of deteriorated concrete and recoating of the isolation stoplog gains. Reservoir drawdown and downstream flow management were key challenges, requiring careful coordination to satisfy operational, environmental, and constructability constraints. Lessons learned highlighted the importance of phased implementation, risk-informed decision-making, and proactive communication between the dam owner, consultant, and contractor. The Conestogo Dam rehabilitation demonstrates a practical approach to improving reliability and safety management for critical infrastructure while meeting the needs of the community and environment.