The effect of various impurities (B, C, N, C, O, Al, Si, S, and P) on the intrinsic resistance of the Σ3 (111) grain boundary (GB) in tungsten has been investigated using molecular dynamics simulation. The Finnis–Sinclair many-body potential for W, and the so-called ‘environment-sensitive embedding energies’ for the impurities were used. The fracture resistance of the GB has been characterized by computing, in each case, the ideal work of GB separation, the Mode I stress intensity factor and the Eshelby's F1 conservation integral at the onset of crack propagation. The results obtained suggest that pure tungsten is relatively resistant towards GB decohesion; this resistance is further enhanced by the presence of B, C and N. On the other hand, O, Al and Si have a relatively minor effect on the cohesion strength of the GB. In sharp contrast, S and P greatly reduce this strength, thus enhancing the tungsten brittleness. These results have been correlated with the effect of the impurity atoms on the material evolution at the crack tip.