GIT1 is a synaptic scaffolding protein that interacts with various pre- and postsynaptic proteins, and is expressed in various brain regions. To investigate in vivo functions of GIT1, we have generated GIT1 knockout mice using genetrap. Immunoblot analysis revealed that expression levels of βPix, a binding partner of GIT1, were reduced in GIT1 mutant mice. Electrophysiological data showed that the basal synaptic transmission was increased and LTP was reduced in GIT1-/- mice. In behavioral analyses, GIT1-/- mice showed enhanced locomotor activity and lowered anxiety. In addition, GIT1-/- mice showed impaired motor coordination and motor learn. Lastly, spatial learning was impaired in GIT1-/- mice. These results indicate GIT1 is an important regulator of synaptic plasticity, anxiety, and spatial and motor learning.