Advances in our knowledge about the neuropsychological mechanisms underlying core deficits in autism spectrum disorder (ASD) have produced several novel treatment modalities. One of these approaches is modulation of activity of the brain regions involved in ASD symptoms. This study examined the effects of transcranial direct current stimulation (tDCS) over the dorsolateral prefrontal cortex (DLPFC) on autism symptom severity, theory of mind, emotion regulation strategies, and emotional‐behavioral functions in children with ASD. Thirty‐two children (Mage = 10.16, SD = 1.93, range 7–12 years) diagnosed with ASD were randomly assigned to active (N = 17) or sham stimulation (N = 15) groups in a randomized, sham‐controlled, parallel‐group design. Participants underwent 10 sessions of active (1.5 mA, 15 min, bilateral left anodal/right cathodal DLPFC, 2 sessions per week) or sham tDCS. Autism symptom severity, theory of mind, emotion regulation strategies, and emotional‐behavioral functioning of the patients were assessed at baseline, immediately after the intervention, and 1 month after the intervention. A significant improvement of autism symptom severity (i.e., communication), theory of mind (i.e., ToM 3), and emotion regulation strategies was observed for the active as compared to the sham stimulation group at the end of the intervention, and these effects were maintained at the one‐month follow‐up. The results suggest that repeated tDCS with anodal stimulation of left and cathodal stimulation of right DLPFC improves autism symptom severity as well as social cognition and emotion regulation in ASD. Lay Summary Previous research has suggested that targeting core mechanisms underlying cognitive‐emotional and behavioral deficits of autistic children might improve symptoms of ASD. Deficient social and behavioral functioning, impaired theory of mind, and emotional regulation deficits have been identified as core treatment targets for this group. Specific subregions of the prefrontal cortex are involved in these deficits, including hypoactivity of the dorsolateral prefrontal cortex (DLPFC). Upregulation of this area with non‐invasive brain stimulation, namely anodal transcranial direct current stimulation (tDCS), results in improved social and behavioral functioning in children with ASD. Very few studies have however examined the effects of this intervention on theory of mind, emotional regulation, and emotional‐behavioral problems. We examined the effects of anodal tDCS over the left DLPFC (F3), combined with cathodal tDCS over the right DLPFC (F4) on autism symptom severity as well as theory of mind, emotional regulation, and emotional‐behavioral problems of children with ASD. This intervention improved autism symptom severity, specific domains of theory of mind, and emotion regulation. These findings have clinical implications for the treatment of ASD and suggest that targeting core mechanisms underlying socio‐cognitive‐emotional deficits of autistic children using tDCS might improve symptoms of ASD.