Local administration of therapeutic agents with long-term retention capabilities efficiently avoids nonspecific distribution in normal organs with an increased drug concentration in pathological tissue. Herein, we developed an injectable and degradable alginate-calcium (Ca2+) hydrogel for the local administration of corn-like Au/Ag nanorods (NRs) and doxorubicin hydrochloride (DOX·HCl). The immobilized Au/Ag NRs with strong absorbance in the near-infrared II (NIR-II) window efficiently ablated the majority of tumor cells after 1064 nm laser irradiation and triggered the release of DOX to kill residual tumor cells. As a result, injectable hydrogel-mediated NIR-II photothermal therapy (PTT) and chemotherapy efficiently inhibited tumor growth, resulting in the complete eradication of tumors in most of the treated mice. Furthermore, owing to the confinement of the Au/Ag NRs and DOX·HCl within the hydrogel, such treatment exhibited excellent biocompatibility.