First-order quasi-phase-matched intracavity second harmonic generation (ISHG) internal to a 1064-nm-Nd∶YVO4 laser end-pumped by a laser diode (LD) based on MgO-doped stoichiometric periodically poled lithium tantalate (PP-MgO∶SLT) is demonstrated. The PP-MgO∶SLT crystal is 20-mm-long and has a grating period of 7.93 μm (at room temperature), which is periodically poled along the z-axis by using the external electric poling technique. The fundamental and second harmonic waves are of z-polarization to access the largest effective nonlinear coefficient. Using a three-mirror folded cavity design for the Nd∶YVO4 laser, the maximum green light output power of 2.1 W and the conversion efficiency of 19% are achieved at an incident LD pump power of 11 W. The relationship between the conversion efficiency of a single-pass extracavity second harmonic generation (ESHG) in PP-MgO∶SLT and the crystal temperature is theoretically investigated. It is found that the measured acceptance temperature bandwidth of the ISHG is significantly wider than that of the ESHG. In addition, the ISHG curve shows an abrupt decrease in second harmonic power as a function of the crystal temperature, and the corresponding discussion is presented.