The paper presents the results of studies of phase transitions in the mixture of n-alkane C23H48 (n-tricosane) and natural bitumen at various concentrations of components. The initial samples of n-tricosane, natural bitumen, and their mixtures were studied by the light scattering as aqueous dispersions. The hydrodynamic radius of the dispersions measured by the dynamic light scattering method was about 100 nm and did not change over a wide temperature range within the measurement accuracy. The temperatures of melting, crystallization, and rotator phase transitions of paraffin in a mixture were determined from temperature-dependent measurements of the light scattering by the dispersions. The dependence of the supercooling value upon the concentration of n-alkane in the mixture was also determined. A new experimental method of investigation of paraffin phase transitions in oils is proposed.