Baixo Sabor dam, whose construction was completed in 2014, is located in Sabor river, one of the right side tributaries of the Douro river, in the North of Portugal, is a double curvature concrete arch dam 123 m high, engineered and constructed by EDP Produção a company of EDP-Energias de Portugal Group. The first filling of the reservoir took place between February 2014 and April 2016. The dam safety monitoring plan was defined during the design phase. It was implemented considering the most suitable measurement instruments to monitor the behavior of the dam during the first filling of the reservoir and the exploitation period. This paper explains the criteria adopted in the definition of the manual data acquisition system to control both the actions applied on the dam and capture the structural response under static loads. It also describes the automatic data acquisition system that completes and validates the data acquired with the manual data acquisition system and some relevant results are presented. Additionally, the dam was equipped with a vibration based structural health monitoring system, composed by 20 uniaxial accelerometers. This paper also describes the main characteristics of this system and the results obtained during the first filling of the reservoir and initial stage of exploitation. These results include the characterization of the accelerations amplitude and the evolution of the dam modal parameters, being particularly interesting to observe the influence of the water level on the modal parameters and the development of statistical models taking into account this effect.