Pistacia atlantica has an anti-cancer effect due to its essential oil which is the major constituent of P. atlantica. Unfortunately, this essential oil evaporates easily and make it less effective. The current research, therefore, aimed to improve the anti-cancer effect of P. atlantica essential oil (PAEO) in solid lipid nanoparticles (SLN). The chemical components of PAEO were assessed by gas chromatography. PAEO-SLNs were prepared by the probe-ultrasonication method, and their particle size, polydispersity index and zeta potential were determined. Encapsulation Efficiency (EE) and Loading Capacity (LC) of formulations was also calculated. Transmission electron microscopy was employed to determine the morphology of optimal formulation (PAEO-SLN4). Furthermore, the anticancer effects of PAEO-SLN4 against MDA-MB-231 cells were evaluated by cellular assays. The results showed that the type of surfactant and loading of the essential oil had a significant effect on size distribution, zeta potential and the polydispersity index. The encapsulation efficiency (EE%) and loading capacity for PAEO-SLN4 were 97.3% and 9.6%, respectively. The cellular assay demonstrates that PAEO-SLN4 could lead MDA-MB-231 cells to apoptosis. The findings also revealed that PAEO-SLN4 can stimulate apoptosis in MDA-MB-231 cells more than the placebo and free PAEO thereby indicating PAEO-SLN4 to be beneficial in breast cancer treatment.