Introduction SHANK3 mutations are associated with striatal dysfunction in autism spectrum disorder (ASD). We evaluated the effects of electroacupuncture (EA) on autism-like behaviors and striatal neuronal plasticity in Shank3B knockout (Shank3B−/−) mice. Methods Wild-type mice served as controls, and Shank3B−/− mice were assigned to untreated model, EA, or sham EA groups. Behavioral outcomes were assessed in eight mice per group. Sparse neuronal labeling and Western blotting used separate cohorts of six mice per group. Dendritic morphology and spine measures were analyzed at the mouse level, and Sholl analysis accounted for repeated measurements across radius. Results EA increased open-field total distance and reduced self-grooming versus untreated Shank3B−/− mice. Three-chamber analysis supported sociability differences, whereas social novelty showed no significant group × target interaction. EA was associated with greater dendritic volume and area and higher total, stubby, mushroom, and filopodial spine densities. The dendritic-area difference was also observed with sham treatment. Sholl analysis showed a significant radius × group interaction, but no EA-versus-model radius-wise comparison remained significant after Holm correction. EA was also associated with altered striatal postsynaptic scaffold protein expression, including increased right-striatal SAP90/PSD95-associated protein 3. Conclusion EA partially rescued selected behavioral deficits in Shank3B−/− mice, reflected by reduced self-grooming, increased open-field activity, and improved sociability, and was associated with striatal structural and postsynaptic scaffold protein changes. These findings support a potential role for EA in modulating behavioral and striatal plasticity-related phenotypes in Shank3B−/− mice.