Schottky barrier heights (SBHs) at metal gate/LaAlO3 (001) interfaces were studied by using ab initio calculations based on density functional theory. Three kinds of metals, Al, Rh, and Pt, were considered with various interface chemistries on LaAlO3 (001) surface. It was found that the Fermi level of metal gates is not pinned at metal gate/LaAlO3 interfaces. The SBH is largely determined by the interface chemistry. The interface metal up to three layers can ultimately decide the SBH, and the SBH at the metal gate/LaAlO3 interface can be efficiently tuned by including monolayer heterovalent metal at the interface.