A complete reliability evaluation methodology for DC grids has not been developed in detail. This paper presents a novel methodology for assessing the reliability of VSC-HVDC grids. First, a reliability model of a VSC-HVDC system is obtained from reliability parameters based on historical data records of outputs of each component. Then, an N-2 contingency analysis is performed to detect DC grid weaknesses and two types of remedial actions are implemented to maintain the whole system in a stable condition. The remedial actions are applied when a DC system operating limits violation occurs, those include topology changes in the grid and adjustments in the power flow by means of an increase or decrease of power supplied by the converter stations. Furthermore, two sets of new reliability indices are defined. The proposed methodology is applied to perform a reliability assessment of the CIGRE B4 DC grid test system and the results are presented. The numerical results shows the expected behavior, remedial actions are effective for all contingencies, reliability indices are consistent and are complementary to the classic indices. This work is useful for planning and operation of grids based on VSC-HVDC technology.