Integrating the concept of biodegradation and light-triggered localized therapy in a functional nanoformulation is the current approach in onco-nanomedicine. Morphology control with an enhanced photothermal response, minimal toxicity, and X-ray attenuation of polymer-based nanoparticles is a critical concern for image-guided photothermal therapy. Herein, we describe the simple design of cost-effective and degradable polycaprolactone-based plasmonic nanoshells for the integrated photothermolysis as well as localized imaging of cancer cells. The gold-deposited polycaprolactone-based plasmonic nanoshells (AuPCL NS) are synthesized in a scalable and facile way under ambient conditions. The synthesized nanoshells are monodisperse, fairly stable, and highly inert even at five times (250 μg/mL) the therapeutic concentration in a week-long test. AuPCL NS are capable of delivering standalone photothermal therapy for the complete ablation of cancer cells without using any anticancerous drugs and causing toxicity. It delivers the same therapeutic efficacy to different cancer cell lines, irrespective of their chemorefractory status and also works as a potential computed tomography contrast agent for the integrated imaging-directed photothermal cancer therapy. High biocompatibility, degradability, and promising photothermal efficacy of AuPCL NS are attractive aspects of this report that could open new horizons of localized plasmonic photothermal therapy for healthcare applications.