(1) Background: The purpose of this study was to investigate the efficacy and safety of transcutaneous vagus nerve stimulation (t-VNS) in the treatment of primary insomnia. (2) Methods: This is a single center, randomized, double-blind study. A total of 30 patients diagnosed with primary insomnia were randomly divided into two groups to receive 20 Hz t-VNS in either the auricular concha area (treatment group) or periauricular area (control group), twice a day for 20 min during a one-month study period. The effective rate of treatment, defined as a ≥50% reduction of the Pittsburgh Sleep Index Scale (PSQI) after treatment, was compared between the two groups as the primary outcome. Response rate (defined as ≥10% change in the PSQI score), and changes in the Hamilton Anxiety Scale (HAMA) and Hamilton Depression Scale (HAMD) scores were also assessed. (3) Results: After one month of treatment, the PSQI score of the treatment group decreased significantly ( = 0.001). The effective rate of the treatment group (73% vs. 27%, = 0.027) was significantly higher than that of the control group. No statistical differences in changes of HAMA and HAMD scores were detected between the two groups. There were no complications in all patients. (4) Conclusion: T-VNS appeared to be a safe and effective treatment for primary insomnia.