Synaptic plasticity in the striatum is a key mechanism that underlies processes such as reward related incentive learning and behavioral habit formation resulting from drugs of abuse. Key aspects of these functions are dependent on dopamine transmission as well as activation of calcium/calmodulin-dependent protein kinase IIalpha (CaMKIIalpha). In this study, we examined the ability of a recently identified heteromeric complex composed of D1 and D2 dopamine receptors coupled to Gq/11 to activate striatal CaMKIIalpha. Using the dopaminergic agonist SKF83959, which selectively activates the D1-D2 complex, we demonstrated phosphorylation of CaMKIIalpha at threonine 286, both in heterologous cells and in the murine striatum in vivo. Phosphorylation of CaMKIIalpha by activation of the receptor complex required concurrent agonism of both D1 and D2 receptors and was independent of receptor pathways that modulated adenylyl cyclase. The identification of this novel mechanism by which dopamine may modulate synaptic plasticity has implications for our understanding of striatal-mediated reward and motor function, as well as neuronal disorders in which striatal dopaminergic neurotransmission is involved.