Significance Dendritic plateau potentials generated by the activation of clustered excitatory inputs play a crucial role in neuronal computation and are involved in sensory perception, learning, and memory. Current studies largely focus on the genesis of plateau potentials. However, little is known about how somatic and local dendritic inhibitions control dendritic plateau potentials. The conventional view of the effectiveness of local dendritic inhibition relies on shunting inhibition. Moreover, massive excitatory conductance could overweigh the shunting inhibition. Here we describe a form of cell-type–specific dendritic inhibition in the striatal spiny projection neurons, in which the inhibition provides precise control over the amplitude, kinetics, and duration of plateau potentials, and thus the spiking output of spiny projection neurons.