The striatum is composed of medium spiny neurons (MSNs), the only neuronal subtype projecting outside this structure, and small populations of GABA- or acetylcholine-releasing interneurons. These sparse interneurons can broadly modulate MSNs input integration and spiking, controlling striatal output. The main excitatory input to the striatum arises from two corticostriatal populations: intratelencephalic (IT) and pyramidal tract (PT) neurons. However, their specific connectivity to striatal interneurons, as well as the polysynaptic impact that pathway-specific activation has on MSN computations, remains underexplored. Here, using slice electrophysiology, optogenetics and transgenic mice, we found that the activation of PT evokes biphasic signals in MSNs, by eliciting a second excitatory phase impinging immediately after direct corticostriatal excitation. This delayed phase is mediated by striatal cholinergic interneurons that are efficiently recruited by PT, but not by IT inputs. Thus, PT afferents, by selectively activating local microcircuit players, trigger acetylcholine-dependent striatal events, conveying feed-forward excitation to MSNs.