The construction of the steel arched Tsakona Bridge, designed to overpass an active landslide, required several temporary projects. Auxiliary steel towers were used for the erection and welding of the arch segments. Most of them had to be founded in the body of the sliding mass. An automated instrumentation and monitoring system was installed on site providing early warning to the engineers in charge in case large displacements were measured. The real-time recording data provided valuable information about the landslide movements. These monitoring results defined the geotechnical and structural design criteria for the deep foundation of the temporary towers. Several 2D and 3D geotechnical and structural models were created to evaluate the sliding effect on the foundation components, finalize their dimensioning and calculate the required reinforcement. The procedure followed for the design of the temporary deep foundation is described based on the criteria devised using the monitoring system, emphasizing on the continuous feedback between the geotechnical and structural design teams. Several key structural design issues required during construction are also presented.