Biodiesel, defined as mono-alkyl esters of triglycerides, has drawn considerable attention in recent years as a clean and renewable fuel. Density is one of the important properties of biodiesel that strongly affects spray characteristics, fuel atomization, and combustion. Although there exists a number of studies in which some important fuel properties (density, viscosity, flash point, heating value, critical properties, cloud point, latent heat of vaporization, etc.) of pure biodiesels, and biodiesel-diesel fuel blends are investigated at different temperatures, and one-dimensional models are proposed to predict their fuel properties, the comprehensive studies involving (i) the measurement of densities of biodiesel-diesel-alcohol (especially higher alcohols) ternary blends, which have been utilized in diesel engines to improve exhaust emissions (especially NOx-smoke trade-off), under varying temperature and blending ratio of alcohol, and (ii) development of two-dimensional regression models to predict densities of ternary blends have not been performed so far. Therefore, in this study, for eliminating the lack of such studies mentioned above items (i and ii) in the existing literature, waste-cooking oil ethyl ester was synthesized and mixed with commercially available diesel fuel on 20 volume basis. Several alcohols were added to the resulting biodiesel-diesel fuel blend (B20) for preparing ternary blends. The densities of ternary blends were measured at various temperatures. Based on the experimental data, some two-dimensional models were first proposed to quick estimate blend density for a given temperature and alcohol blending ratio. The models were tested against different density data of used cooking oil methyl ester-diesel-bioethanol ternary blends previously reported in the literature. Graphic representations of density as a simultaneous function of temperature and blending ratio in three-dimensional plots were firstly given in the literature. Finally, the variations in constant density lines showing different gradient regions were also firstly given. According to the authors' knowledge, the novelties of this study are the derivation of two-dimensional models and investigation of changes of constant density lines for ternary blends including biodiesel, diesel, and various alcohols.