In the current study, we aim to solve a group decision‐making problem on the basis of expert judgment with consideration of both global and local ignorance in system safety assessment. When data are acquired from various sources, especially subjective ones, the estimation of the data's precise value is challenging. In such a case, the basic belief assignment (bba) function is utilized to cope with the decision‐making procedure on the basis of Dempster‐Shafer theory (DST). DST, as an effective tool for manipulating inaccurate values, stills is not adequate to obtain the optimum values under the consideration of global and local subjective ignorance. To address the aforementioned subjects in this study, an innovative heuristic approach using a multiobjective programming model is introduced to derive the optimal values (bba) in the system safety assessment. An illustrative example is provided in detail to show the applicability and feasibility of the introduced heuristic approach.