Thermal effects are investigated using laser interferometric and infrared thermometric techniques in diode-end-pumped solid state lasers operating under lasing and nonlasing states. The laser interferometry provides high resolution to determine the optical path difference (OPD) induced by thermal effects of the crystal. The infrared thermometer measuring the temperature distribution at the end pump face is proposed to evaluate the thermal lensing power induced by the index part. It is found that the temperature variations across the crystal face under nonlasing operation increase 20 to 27% compared with lasing conditions in Nd:YVO4 crystals. Thermal lensing power under the actual lasing condition is measured to be 0.2 m-1 to 2.1 m-1 with the pump power ranging from 1 to 8.3 W; the index part takes the proportion of about 59% in the total thermal lensing effect for end-pumped Nd:YVO4 lasers.