The Doppler effect for 235U-enriched UO2 fuel pellets has been measured by the Pulsed Activation Doppler (PAD) technique in a TRIGA reactor. A combination of static electrical preheating and pulsed fission heating during irradiation was used to perform the measurements at temperatures extending from 300 K to the melting point of UO2 (3115 K). The 235U enrichment in the experimental samples investigated ranged from 0.22 to 12% by weight. Measurements were made at the highest temperatures ever achieved in Doppler experiments and represent the first activation Doppler measurements under partially molten conditions of UO2. Two sizes of pellets were used in the work, with nominal surface-to-mass ratio values of 0.63 and 1.08 cm2/g, respectively. The experimentally determined values of the Doppler ratio were in good agreement with resonance integral ratios determined from GAROL calculations and extrapolations of the low-temperature Hellstrand correlation. Because the technique involved transient heating, an equivalent static temperature (θeff) was defined for each experimental pellet. Explicit correlations for the Doppler ratio as a function of the parameter were determined from the present data. It is shown that a linear function in the parameter adequately describes the behavior of the data.