Multifunctional nanomaterials open an avenue for the integration of cancer treatment and diagnosis, trending towards the clinical application of nanomedicines in future. Herein, we synthesized biocompatible CuCo2S4 nanocrystals (NCs) via a simple reflux method and unitized them as a new theranostic platform, where an intense near-infrared (NIR) absorption offers the CuCo2S4 NCs a perfect photothermal performance and photoacoustic (PA) imaging ability; the magnetic characteristic of Co allows them to serve as an enhanced magnetic resonance (MR) contrast agent. The in vitro and in vivo experiments demonstrated their good biocompatibility, non-toxicity and perfect photothermal conversion performance and further confirmed that HeLa tumors could be effectively thermal-ablated upon the assistance of the CuCo2S4 NCs. This work introduces the first bioapplication of the CuCo2S4 NCs and promotes theranostics based on other ternary compounds.