Combination therapy integrated with nanotechnology offers a promising alternative for breast cancer treatment. The inclusion of pequi oil, anacardic acid (AA), and docetaxel (DTX) in a nanoemulsion can amplify the antitumor effects of each molecule while reducing adverse effects. Therefore, the study aims to develop pequi oil-based nanoemulsions (PeNE) containing DTX (PDTX) or AA (PAA) and to evaluate their cytotoxicity against triple-negative breast cancer cells (4T1) in vitro. The PeNE without and with AA (PAA) and DTX (PDTX) were prepared by sonication and characterized by ZetaSizer^® and electronic transmission microscopy. Viability testing and combination index (CI) were determined by MTT and Chou-Talalay methods, respectively. Flow cytometry was employed to investigate the effects of the formulations on cell structures. PeNE, PDTX, and PAA showed hydrodynamic diameter < 200 nm and a polydispersity index (PdI) of 0.3. The association PDTX + PAA induced a greater decrease in cell viability (~70%, p < 0.0001) and additive effect (CI < 1). In parallel, an association of the DTX + AA molecules led to antagonism (CI > 1). Additionally, PDTX + PAA induced an expressive morphological change, a major change in lysosome membrane permeation and mitochondria membrane permeation, cell cycle blockage in G2/M, and phosphatidylserine exposure. The study highlights the successful use of pequi oil nanoemulsions as delivery systems for DTX and AA, which enhances their antitumor effects against breast cancer cells. This nanotechnological approach shows significant potential for the treatment of triple-negative breast cancer.