Theranostics that combines the disease diagnosis with treatment is of promising application in the foreground of personalized medicine to achieve a precise treatment with minimum side effects. In this work, we strategically designed a “four-in-one” theranostic nanoplatform for realizing the desired imaging-guided phototherapy, in which functions of fluorescent imaging, photoacoustic imaging tomography (PAT), photothermal therapy (PTT) and photodynamic therapy (PDT) were implemented by bioconjugated MoS2 nanosheets. The protagonist of MoS2 is a light-harvesting material in the near-infrared (NIR) region, which would produce localized hyperthermia at the tumor site to trigger the photothermal therapy effect for the tumor ablation as well as a PAT signal to depict the tumor concurrently upon NIR excitation. To our surprise, MoS2 has been found to be a photosensitizer for the cancer PDT treatment as well. Moreover, bovine serum albumin (BSA) decoration on MoS2 has been made to improve biocompatibility, which also allowed further conjugation with a fluorescent molecule of Cy5.5 to endow the overall nanoplatform with fluorescence imaging and monitoring features. On the basis of the above characters, great successes in cancer imaging and tumor photoablation were achieved in both in vitro and in vivo experiments. Innovatively, B-ultrasonography and MRI imaging were employed to monitor the elimination process of solid tumor after treatment, which clearly revealed a liquefaction necrosis process for rehabilitation. In short, MoS2 represents a nanoplatform of this work and manifested huge advantages in the cancer theranostics.