Red palm oil (RPO) contains carotenoids, which are highly beneficial to human health owing to their antioxidant properties. RPO has low stability during storage; hence, it must be formulated in a submicron emulsion. This study aims to enhance the formulation of RPO submicron emulsion using a D-phase emulsification method with D-optimal mixture design methodology. The effect of the concentration of RPO (45%-60%), sucrose palmitate (10%-25%), and glycerol (25%-40%) on globule size, polydispersity index (PDI), and zeta potential was investigated. The optimum formula was then subjected to a short-term accelerated stability test at 40 °C for 7 days, comparing the carotenoid retention in the submicron emulsion versus bulk RPO and characterized using Transmission Electron Microscopy (TEM) and Fourier Transform Infrared Spectroscopy (FTIR). The data showed that an increase in component concentrations below a preset limit resulted in a significant change in response cubically, thus yielding high coefficients of determination (R²>0.96) for all three responses (p<0.05). The optimum formula was achieved with components in the proportions of 55.70% RPO, 12.05% sucrose palmitate, and 32.25% glycerol, with globule size, PDI, and zeta potential of 184.20±2.75 nm, 0.079±0.011, and-40.40±0.53 mV, respectively. Notably, the short-term stability study showed that the submicron emulsion system significantly improved carotenoid stability compared to bulk RPO after 7 days at 40 °C. The TEM study confirmed that the emulsion globules form spheres and are uniformly distributed, whereas the FTIR study showed no chemical interactions. In summary, the D-phase emulsification method effectively produced a stable RPO submicron emulsion. © 2026, Penerbit Universiti Kebangsaan Malaysia. All rights reserved.