Autism Spectrum Disorders (ASD) are a range of neurodevelopmental disorders, characterized by behavioral and neuronal anomalies. Phelan-McDermid Syndrome (PMS) constitutes a specific neurodevelopmental disorder exhibiting ASD-like behaviors, caused by mutations or deletions of SHANK3 gene. Mice lacking the SHANK3 gene are widely considered a reliable model to study PMS, since they show autism-like behaviors and sensory deficits, such as aberrant whisker-dependent texture discrimination and local hyperactivation of the barrel-field cortex. These local alterations mirror dysfunctions of the entire cortical network, as evidenced by the disrupted functional connectivity (FC). Transcranial Direct Current Stimulation (tDCS) is a noninvasive brain stimulation procedure with high translational potential as a tool to modulate sensory deficits in PMS. Here we applied a cathodal mild electric current to induce neuronal inhibition and assessed short- and long-term effects of tDCS on the sensory-evoked activity in Shank3 haplo-insufficient mice (Shank3b HET). To this aim, mice were transfected with a calcium indicator via PHP.eB transfection, enabling the monitoring of cortical activity in the awake state before and across several time points after a 20-minute session of 0.2 mA cathodal tDCS. Preliminary results indicate an acute reduction of barrel-field activity in response to whisker stimulus, sustained until 1 month from the tDCS session. Cathodal tDCS also induces alteration of cortical FC in Shank3b HET mice. Taken together, these results support the effectiveness of tDCS in recovering sensory deficits and FC alterations in PMS.