Chemotherapeutic drugs have shown some limitations in anti-tumor treatment, such as drug resistance, high toxicity and limited regime of clinical uses. Natural products have attracted extensive attention as potential source of unmodified chemical compounds for disease treatment. Withaferin A (WA) has the potential to inhibit multiple human tumors, but it is hardly available for oral administration due to its low water solubility and its side effects. We developed a methoxy poly(ethylene glycol) (mPEG) conjugated poly(d,l-lactide-co-glycolide) (PLGA) drug carrier particles to encapsulate WA for pancreatic cancer treatment. The results showed that WA does not lose its physicochemical properties after encapsulation, and our drug carriers are completely degraded within 1 month. We used the WA-loaded mPEG-PLGA particles for pancreatic cancer cell treatment where it exhibited stronger inhibition than free drug (WA) at the early treatment stage. Our formulation of the drug carriers provides an efficient encapsulation of WA that allows it bonding with heat shock proteins, thereby reducing the expression of AKT and CDK4 proteins to induce apoptosis in cancer cells. Together, our data demonstrate that mPEG-PLGA loaded with WA can achieve the design goals for cancer therapy given its advantages of sustained release and degradation property to reduce the side effect of WA, which provides a possibility for WA to be used in clinical applications.