III-V compound semiconductors are currently being investigated as replacements for Si in future metal-oxide-semiconductor field effect transistor (MOSFET) technologies. GaAs is a good candidate as a buffer layer material for integration of alternative channel materials such as InGaAs and InAs on Si wafers. One barrier to good quality III-V epitaxy on Si is the formation of antiphase domain boundaries (APBs) due to the polar-on-nonpolar growth. High-temperature pre-growth bakes and off-cutting of the wafer typically used to eliminate APBs in III-V layers grown on Si are incompatible with conventional CMOS processing. Thus, the influence of growth conditions on APB propagation to facilitate self-annihilation is critical to understand. It has been shown that a higher bulk growth temperature can influence the preferred plane of propagation for APBs in GaP on Si(001) leading to enhanced annihilation of APBs. However, this effect has yet to be examined for GaAs on Si(001) and the effect on APB annihilation rate as a function of growth temperature has not been quantified. In this study, nominally 800 nm thick GaAs films were grown on exact-cut 300 mm Si(001) wafers by an Applied Materials III-V metal-organic chemical vapor deposition (MOCVD) system. The films were grown in a multi-step manner. The initial growth stages were identical for all samples in order to obtain similar starting APB densities. The growth temperature of the final stage was varied to investigate the effect on APB annihilation. Depth profiles of APB density for each sample were obtained using a combination of a bulk GaAs chemical etchant and an APB-selective chemical etchant and examination with a scanning electron microscope to determine the respective APB annihilation rates. The evolution of APBs in cross-section was examined using transmission electron microscopy. It was found that increasing the growth temperature of the final stage by 80 °C increased the annihilation rate of APBs in the GaAs films by approximately a factor of 5. The associated activation energy for the increase in APB annihilation rate was calculated to be 1.1 eV. There was no significant difference in APB annihilation rate after the 80 °C increase. This result is of relevance for the selection of appropriate growth conditions and considerations of thermal budgets for future CMOS processing with III-V based devices.