Curcumin as a safe traditional compound has various benefits such as anticancer activities. However, low solubility in water is a problem. Herein, curcumin encapsulated in polymersome nanoparticles (CPNs) have been developed, the physicochemical properties have been evaluated, and cytotoxicity effects on HT29 cells were evaluated by MTT assay and annexin V/PI staining. The expression of stemness markers including CD44, CD133, and CD24, as well as miRNAs (miR‐126, miR‐34a, miR‐21, miR‐155, miR‐221, and miR‐222) and some potential targets, was evaluated in CPNs‐treated and untreated cells. Physicochemical analysis confirmed the encapsulation of curcumin in polymersomes and showed a spherical shape, an appropriate mean size of 259.5±1.5 nm, the acceptable polydispersity index of ~ 0.465, and the zeta potential of (‐8.74±0.2), as well as long‐term storage of CPNs at 4°C. According to the result, CPNs with the IC50 of 14 μg/ml increased apoptosis and induced S arrest in treated cells. Flow cytometry analysis showed the decrease in cancer stemness markers. RT‐qPCR analysis identified the downregulation of miR‐21, miR‐155, and miR‐221/222, as well as upregulation of miR‐34a, miR‐126, and deregulation of some apoptotic targets such as P53, CASP9, CASP8, CASP3, BAX, and BCl‐2 in CPNs‐treated cells. As a result, CPNs can be a safe and effective complementary agent to diminish cancer stem cells and tumor recurrence in colorectal cancer therapy.