The objective of this study was to evaluate the effectiveness and tolerability of citalopram versus citalopram plus paliperidone combination therapy in patients with somatoform disorders (SDs). In this 6-week, randomized, fixed-dose study, 60 patients with SD (ICD-10 F45.0), undifferentiated SD (F45.1), and somatoform autonomic dysfunction (F45.3) were randomly assigned to receive citalopram (20 mg/day) with or without paliperidone (3 mg/day). Four scales were used to evaluate effectiveness and tolerability at baseline and at the end of the second, fourth, and sixth week after treatment: Somatoform Disorders Screening Symptoms-7 (SOMS-7), Hamilton Anxiety Scale (HAMA), 17-item Hamilton Depression Scale (HAMD-17), and Treatment Emergent Symptom Scale (TESS). The rater was blinded to the kind of treatment patients received. (i) In the intention-to-treat population (N = 51), the overall response ratio (50% reduction in SMOS-7 scores) was significantly higher in the citalopram-paliperidone group compared with the citalopram group after a 6-week treatment (71.4 vs. 38.10%, χ² = 4.71, P = 0.03). (ii) The SOMS-7 and somatic subscore of the Hamilton Anxiety Scale (HAMA-SOM) total score of the citalopram plus paliperidone group decreased more significantly than that of the citalopram group, and a significant difference could be observed at the end of 4 weeks of treatment. (iii) There was no significant difference between the two groups in adverse effects, and no serious adverse event was reported in both groups. Our findings indicate that a combination with paliperidone is significantly better than monotherapy with citalopram whether synergistic or add-on for patients with SDs. Our results call for future studies with larger sample sizes and a longer duration to draw more definitive conclusions.