In this study, we fabricated a bicrystal of SrTiO3 containing a I pound = 9, [110]/{221} symmetric tilt grain boundary (GB) and its atomistic structure was directly observed by transmission electron microscopy (TEM) and scanning TEM (STEM). We theoretically estimated the most stable structure by first principles calculations, and by combining this with TEM images determined the atomistic structure of the I pound = 9 grain boundary. We found that when the grain boundary is slightly tilted from the coincident site lattice (CSL) orientation, displacement shift complete (DSC) dislocations are introduced at the grain boundary to accommodate the misorientation between the two adjacent crystals while the most stable atomic structure remains unchanged.