The thermal effects of diode-end-pumped Nd:YVO4 and Nd:YAG lasers are analyzed by a 2-D analytical model and a 3-D numerical model, respectively. The characteristics of the Nd:YVO4 and Nd:YAG rods are comparatively discussed, including temperature distributions and thermal lensing effects. The model quantitatively separates the end effect from the index parts. Under the same pump configuration, we find that the temperature increase in the Nd:YVO4 laser was 2 times larger than those in the Nd:YAG laser, while the thermal lensing coefficient of Nd:YAG was 27% higher than that of Nd:YVO4. We also conclude that a good roundness of the Nd:YVO4 laser beam profile is expected because nearly symmetric thermal lensing in the a and c axes is predicted from our modeling and measurement. Correspondingly, we perform experiments that are in good agreement with theoretical modeling for the thermal lensing of diode-pumped Nd:YVO4 and Nd:YAG lasers.