Abstract The partitioning, rotational correlation times (τR), and electron spin–lattice relaxation times (T1e) of various small spin probes in dispersions of a triglyceride membrane were investigated using CW-ESR (continuous wave-electron spin resonance) and SR (saturation recovery) spectroscopies. The partitioning of small spin probes, DTBN and TEMPO, in the aqueous and vesicle phases was determined by an ESR linewidth simulation. The results suggest that DTBN and TEMPO have a similar partitioning in the vesicle phase throughout the temperatures studied. The simulation results were quite different from those of conventional intensity analysis. In addition, the rotational correlation times of the vesicle phase for both probes varied from 1.2 × 10−10 to 4.9 × 10−10 s. The activation energy (Ea) calculated from the τR values in the phase was ∼29 [kJ/mol] for the probes. The thermal behavior based on the Ea value is that in between the 12-doxylstearic acid (12-DSA) and 16-DSA moieties of the membrane. The longer τR and shorter T1e (∼0.33 μs) values of DTBN in the vesicle phase were obtained, and could be attributed to the probe environment in the membrane. Thus, the present experimental evidence has provided a qualitative understanding of the probe dynamics as well as the membrane properties.