An injectable multifunctional hydrogel based on an engineered coiled-coil polypeptide, Ag2S quantum dots (QDs), and paclitaxel (PTX) has been developed for sustained chemo-photothermal therapy. Oil-soluble Ag2S QDs and PTX were first loaded into nanogels formed with engineered polypeptide PC10A by ultrasonic treatment to prepare PC10A/Ag2S QD/PTX nanogels. The multifunctional PC10A/Ag2S QD/PTX hydrogels were prepared by dissolving the PC10A/Ag2S QD/PTX nanogels into the PC10A hydrogel. The PC10A/Ag2S QD/PTX hydrogel can be injected directly into the site of tumors. In vitro and in vivo toxicity results showed that the PC10A/Ag2S QD/PTX hydrogel presented excellent biocompatibility. Compared with single near-infrared photothermal therapy and chemotherapy, the combined therapy could effectively suppress the growth of SKOV3 ovarian carcinoma tumor. In addition, real-time monitoring of the in vivo degradation of the PC10A/Ag2S QD/PTX hydrogel was achieved by near-infrared fluorescence imaging and photoacoustic imaging. These results demonstrated that this injectable multifunctional PC10A/Ag2S QD/PTX hydrogel has the potential as a theranostic platform for sustained cancer treatments.