Abstract Background Around 15% of the Hong Kong population was found to suffer from overactive bladder (OAB), but the current available treatments, such as medication, behavioral therapy and physical therapy are unsatisfactory. Previous studies have suggested that acupuncture may have promising effect for OAB, but some limitations on the study design render the evidence questionable. This study aimed to evaluate the effectiveness and safety of acupuncture treatment for patients with OAB in Hong Kong. Methods One hundred patients with OAB were enrolled. The patients were randomized to receive either active acupuncture or sham needle intervention twice a week for 8 consecutive weeks, and had a follow-up consultation 12 weeks after the completion of acupuncture intervention. The primary outcome assessment was the 3-Day Voiding Diary, which records daytime and night-time urinary frequency and symptoms, at the baseline, the end of the 8-week intervention and 12 weeks after acupuncture intervention. Secondary outcomes included Urine NGF level, Incontinence Impact Questionnaire (IIQ-7) and Urogenital Distress Inventory (UDI-6), as well as Overactive Bladder Symptom Score (OABSS). Results After 16 sessions of treatment, when compared with the baseline, both active and sham acupuncture significantly reduced the frequency of urgency urinary incontinence (UUI), daytime and night-time urinary frequency as well as the scores of IIQ-7, UDI-6 and OABSS. Moreover, the treatment effects could last for at least 3 months. However, no significant difference in frequency of UUI and daytime urinary frequency was found between the active and sham acupuncture groups. On the other hand, the night-time urinary frequency decreased more significantly during the treatment and follow-up in the active acupuncture group than in the sham control group after controlling baseline night-time urinary frequency. Urine NGF level could not be detected by ELISA method in our experiments. Conclusion This study suggests a beneficial effect of acupuncture on improving OAB symptoms. Both active and sham acupuncture treatment were able to improve the symptoms of frequency of urgency urinary incontinence, and the daytime and night-time urinary frequency, while only mild adverse effects were found. This project was unable to establish the specific effect of acupuncture for OAB. Trial registration Chinese Clinical Trial Registry, ChiCTR-INR-16010048. Registered on 29 Nov 2016.