Palm oil (PO) is utilised for food such as cooking oil and non-food such as for making creams, soaps and detergents. It contains various unsaturated and saturated fats, vitamin E, and β-carotenes. This study aimed to clarify the influence of PO plus photobiomodulation (PBM) on leukaemia (K562 cells) proliferation. Cells were treated with various concentrations of PO, PBM at wavelength 655 nm with 1, 2, 3 and 6 J/cm², and PO in pre- and post-irradiation with PBM. The proliferation of cells was investigated by MTT assay, morphologic microscopy and flow cytometry. The amount of reactive oxygen species (ROS) was also determined. Cells were subjected to PO and then PBM in the presence of NAC (N-acetylcysteine) to assess the involvement of ROS in cell growth. PO can diminish the viability of K562 cells significantly. PBM did not have a remarkable effect on the viability of cells. Pre-treatment with PO and then irradiation with 1 J/cm² energy could induce apoptosis through intracellular ROS generation and had effective antiproliferative impacts on cells compared to those which acquired separate treatments with laser irradiated alone or PO alone. Thus, our research offers new strategies to utilise PO in combination with PBM in cancer treatment.