The kernel oil of the Attalea phalerata Mart. Ex Spreng (Acurí) is traditionally used in several Latin American countries to treat respiratory problems, inflammation, and fever. However, it cannot be found on the literature any attend to use this oil in pharmaceutical formulation. In this paper, it was developed Acurí oil-loaded nanocapsules, and it was evaluated the cytotoxicity against cancer cells, the antinflammatory activity and the oral acute toxicity in rats. Acurí oil contains lauric acid as the predominant saturated fatty acid (433.26 mg/g) and oleic acid as the main unsaturated fatty acid (180.06 mg/g). The Acurí oil-loaded nanocapsules showed a size of 237 nm, a polydispersity index of 0.260, and a high ζ-potential of −78.75 mV. It was obtained an encapsulation efficiency of 88.77%, and the nanocapsules remain stable on the shelf for 180 days. The nanocapsules showed a rapid release profile (98.25% in 40 minutes). Nanocapsules at a dose of 10 mg/kg exhibit an anti-inflammatory effect similar to indomethacin at the same dose. The nanocapsules showed excellent antiproliferative effect and selectivity index against prostate tumor cells (IC₅₀ 2.09 µg/mL, SI=119.61) and kidney tumor cells (IC₅₀ 3.03 µg/mL, SI=82.50). Both Acurí oil and Acurí oil-loaded nanocapsules are nontoxic at a dose of 2000 mg/kg. Additionally, they reduce serum triglyceride and total cholesterol levels in rat and could find application in nutraceutical formulations. The Acurí oil-loaded nanocapsules emerge as a promising candidate for new antitumor therapies.