This work describes the development, implementation, and validation of an index (Bench Stability Index, BSI) to evaluate the design and construction of bench berms in open pit mines based on the rock engineering system (RES). Stability at bench scale was initially defined using ten parameters for the RES interaction matrix. To implement and verify the RES-based stability index, we evaluated 5993 m of walls built in a bench-berm geometry for five different lithological units in an existing Chilean open pit mine. Results obtained with the proposed Bench Stability Index is compared with conventional systems for evaluating bench design achievement (factor of condition and factor of design) and with the georadar monitoring measurements. Comparison of the BSI using data that is available during the design stages of the project indicated a good consistency with the results obtained from the two other methods traditionally used in stages of mine construction and production. The contribution of the BSI approach is that it allows the rock mass response of the bench-berm system to be inferred prior to the construction stage, therefore improving the decision-making during the mine-design phase and supporting the early establishment of mitigation measures to comply with production plans.