Abstract This paper describes the planning and execution of an integrated Plug and Abandonment (P&A) operation on a well located in the middle of the remote Magdalena River in Colombia. This project was executed using a combination of specialized technologies from multiple service lines, including well control services, Hydraulic Workover (HWO), wireline, cementing, fluids services, and completion tools. An engineering study and river support barges were also a requirement, along with the design, build, and installation of specialist equipment, such as a support structure for the high fluctuations in water levels. The planning and execution of this particular abandonment made this a unique operation, believed to be the first of its kind in the world. This project was performed in a very complex environment where river conditions and water depths allowed only a limited operational window. Since the well had been shut in for 40 years and was located in the middle of the Magdalena River, well integrity was another key concern. Other challenges included designing and implementing a customized structure suitable for supporting HWO operations in a shallow-water environment, developing a complex readiness process that included civil works (structure design and construction), a social approach, local content development, and environmental permits and licenses. Despite the many environmental and well integrity challenges, comprehensive planning and preparation activities were key in successfully executing this under-river P&A project. All phases (including well intervention, mobilization, and demobilization) were accomplished with no recorded HSE or service quality issues. All the activities were executed without impacting the river, fauna, and the environment. This project was also delivered 6% ahead of schedule, 35 days in total and in full compliance with contract requirements and local regulations. This highly complex project represents an achievement for the well operator and service company as it is believed to be the first of its kind in Colombia and worldwide. This success story is a reference for future abandonment operations under similar conditions expected to be required in the Magdalena River in Colombia.