We present the results of first-principles electronic structure investigations, using spin-polarized density-functional-theory, of the electronic and geometric structures of the joined edges formed between two domains of single-layer MoS2. We find joined-edge defects to be metallic or half-metallic wires in the considered models. More interestingly, we find the signature of magnetism in the joined-edge defect formed between two Mo-terminated (1010) edges. Analysis of the geometric structure leads us to the conclusion that certain joined-edge defects undergo (2 × 1) reconstruction.