This study aimed to develop and evaluate sustained-release (SR) long-acting oral nanocomposites in-situ gelling films of resveratrol (Rv) to treat colorectal cancer. In these formulations, Rv-Soy protein (Rv-Sp) wet granules were prepared by the kneading method and then encapsulated in the sodium alginate (NA) dry films. The prepared nanocomposite in-situ gels films were characterized using dynamic light scattering, Fourier-transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The optimized formulations were further evaluated based on drug encapsulation efficiency, pH-drug release profile, swelling study, and storage time effects. The optimized formulation was tested for its anticancer activity against colorectal cancer cells using the cytotoxicity assessment, apoptosis testing, cell cycle analysis, gene expression analysis, and protein estimation by the reverse-transcriptase polymerase chain reaction and enzyme-linked immunosorbent assay methods, respectively. The optimum film showed encapsulation efficiency of 97.87% ± 0.51 and drug release of 14.45% ± 0.043 after 8 h. All physiochemical characterizations confirmed, reasoned, and supported the drug release experiment’s findings and the encapsulation assay. The Rv nanocomposite formulation showed concentration-dependent cytotoxicity enhanced apoptotic activity as compared to free Rv (p < 0.05). In addition, Rv nanocomposite formulation caused a significant increase in Bcl-2-associated protein X (Bax) and a decrease in expression of B-cell lymphoma 2, interleukin 1 beta, IL-6, and tumor necrosis factor-alpha (Bcl2, IL-1β, IL-6, and TNF-α respectively) compared to that of free Rv in HCT-116 cells. These results suggest that long-acting Rv nanocomposite gels could be a promising agent for colorectal cancer treatment.