A climbing formwork system for mass concrete construction, in particular for building a dam or for hydropower industry, comprising: - a movable panel defining a wall of the climbing formwork system; said movable panel having an inner surface facing a filling volume of the climbing formwork system for containing the concrete and an outer surface facing an external environment; - a track having a main extension along a longitudinal direction extending along a direction of climbing and positioned at least partially inside said filling volume of the climbing formwork system; said track comprising a sliding channel closed with respect to the filling volume and having a longitudinal slit extending along the longitudinal direction; said slit being configured to realize a communication between said sliding channel and said external environment or said movable panel; wherein an orthogonal section of said track, with respect to the longitudinal direction, is "C-shaped" so as to said slit is realized between two opposite legs of the "C-shape"; - a climbing element slidingly inserted in said sliding channel and configured to slide along said longitudinal direction; said climbing element comprising a connection portion projecting through said slit and configured to be connected with a portion of said movable panel; - fastening elements operatively connected between said connection portion of the climbing element and the movable panel in order to maintain the movable panel fixed to the climbing element in a union condition; wherein said fastening elements in the union condition are configured to arrange said climbing element against said two legs and to arrange said two legs against said movable panel so that said two legs define a sliding surface for the sliding of said climbing element along said longitudinal direction. - a movable panel defining a wall of the climbing formwork system; said movable panel having an inner surface facing a filling volume of the climbing formwork system for containing the concrete and an outer surface facing an external environment; - a track having a main extension along a longitudinal direction extending along a direction of climbing and positioned at least partially inside said filling volume of the climbing formwork system; said track comprising a sliding channel closed with respect to the filling volume and having a longitudinal slit extending along the longitudinal direction; said slit being configured to realize a communication between said sliding channel and said external environment or said movable panel; wherein an orthogonal section of said track, with respect to the longitudinal direction, is "C-shaped" so as to said slit is realized between two opposite legs of the "C-shape"; - a climbing element slidingly inserted in said sliding channel and configured to slide along said longitudinal direction; said climbing element comprising a connection portion projecting through said slit and configured to be connected with a portion of said movable panel; - fastening elements operatively connected between said connection portion of the climbing element and the movable panel in order to maintain the movable panel fixed to the climbing element in a union condition; wherein said fastening elements in the union condition are configured to arrange said climbing element against said two legs and to arrange said two legs against said movable panel so that said two legs define a sliding surface for the sliding of said climbing element along said longitudinal direction.