In this investigation, polyacrylamide (PAAm) as the flexible network is introduced to enhance the mechanical strength of hyaluronic acid–gelatin (HA–Gel) hydrogels by interpenetrating polymer network (IPN). The structure, mechanical property, and rheology property of the IPN hydrogels are investigated. It is found that the compressive strength of the HA–Gel/PAAm IPN hydrogels has increased five times higher than that of HA–Gel hydrogels. Rheological test demonstrates that elastic moduli (G0) and viscous moduli (G00) of HA–Gel/PAAm IPN hydrogels increase 100 times higher than those of HA–Gel hydrogels. Moreover, the HA–Gel hydrogels are fractured under the low compressive stress, whereas HA–Gel/PAAm IPN hydrogels are not broken under the high compressive stress. It is envisioned that the IPN hydrogels will be an effective approach to enhance the mechanical strength and broaden the range of hydrogels’ applications.