Developing functional hybrids of globular proteins and synthetic polymers into multipurpose tough hydrogels remains challenging. Here, we propose a new strategy combining double-network and protein misfolding concepts to create diverse protein–polymer double-network (DN) hydrogels with both high bulk and interfacial toughness. The method integrates an intrinsic heat-induced protein denaturation/aggregation feature and a double-network concept, which produces different bovine serum albumin (BSA)-based DN hydrogels with hybrid physical–chemical cross-linking or fully physical cross-linking to achieve a high modulus of 252–1199 kPa, high strength of 0.24–0.48 MPa, high fracture energy of 3.56–16.88 MJ/m³, high extensibility of 7.7–79.9 mm/mm, fast self-recovery (stiffness/toughness recovery of 94/80% after heat treatment at 80 °C for 30 min), and strong surface adhesion to various nonporous solid surfaces (interfacial toughness of 1176–2827 J/m²). Such tough and adhesive protein–polymer hydrogels have great potential for different applications, such as artificial soft tissues, flexible electronics, and wearable devices.