Background: Clinical advantages of the cranial electrical stimulation (CES) are not yet clear. Objective: The objective of the study was to know the effects as a result of the CES intervention for the treatment of insomnia symptoms, anxiety, and depression. Method: Twenty-four individuals agreed to participate in the study, all of them with initial insomnia diagnosis (ISDC-2), with an average age of 32.10 (± 14.24) years old (58% women), distributed in control (n = 11) and experimental group (n = 13). The intruments used were Beck's depression inventory, State-Trait Anxiety Inventory, the Insomnia Severity Index, and the Insomnia Symptoms Questionnaire. A CES device (Fisher Wallace-100) was given to each participant for its use at nights and mornings (20 min each session) for 10 days. Results: Insomnia symptoms decreased significantly in both the control and experimental groups (p < 0.01), but only in the experimental group there was a significant reduction in the severity of insomnia (p < 0.05). According to the effect size (Cohen's d), the experimental group had a larger effect in the insomnia severity and a moderated effect for anxiety and depression. The placebo group had a small effect in anxiety and a medium in insomnia and depression. Conclusions: The CES effect is superior to placebo to reduce the insomnia severity, but it is no different from placebo for anxiety and depression symptoms.