Synaptic adhesion molecules mediate synapse formation, maturation and maintenance. These proteins are localized at synaptic sites in neuronal axons and dendrites. These proteins function as a bridge of synaptic cleft via interaction with another synaptic adhesion molecules in the opposite side. They can interact with scaffold proteins via intracellular domain and recruit many synaptic proteins, signaling proteins and synaptic vesicles. Scaffold proteins function as a platform in dendritic spines or axonal terminals. Recently, many genetic studies have revealed that synaptic adhesion molecules and scaffold proteins are important in neurodevelopmental disorders, psychotic disorders, mood disorders and anxiety disorders. In this review, fundamental mechanisms of synapse formation and maturation related with synaptic adhesion molecules and scaffold proteins are introduced and their psychiatric implications addressed.