Chemically linked Double network (DN) hydrogels display extraordinary mechanical attributes but mostly suffer from poor self-healing property and unsatisfactory biocompatibility due to the irreversible breaks in their chemical-linked networks and the use of toxic chemical crosslinking agents. To address these limitations, we developed a novel κ-carrageenan/polyacrylamide (KC/PAM) DN hydrogel through a dual physical-crosslinking strategy, with the ductile, hydrophobically associated PAM being the first network, and the rigid potassium ion (K+) cross-linked KC being the second network. The dual physically cross-linked DN (DPC-DN) hydrogels with optimized KC concentration exhibit excellent fracture tensile stress (1320 ± 46 kPa) and toughness (fracture energy: 6900 ± 280 kJ/m3), comparable to those fully chemically linked DN hydrogels and physically-chemically cross-linked hybrid DN hydrogels. Moreover, owing to their unique dual physical-crosslinking structures, the KC/PAM hydrogels also demonstrated rapid self-recovery, remarkable notch-insensitivity, self-healing capability, as well as excellent cytocompatibility towards stem cells. Accordingly, this work presents a new strategy towards fabricating self-repairing DPC-DN hydrogels with outstanding mechanical behaviors and biocompatibility. The new type of DN hydrogels demonstrates strong potentiality in many challenging biomedical applications such as artificial diaphragm, tendon, and cartilage.