Aim To compare treatment success rate in terms of improvement of bladder overactivity between unilateral and bilateral sacral neuromodulation testing. Methods A multicentric, parallel, randomized, open pilot trial (October 2012‐September 2017) was conducted. Participants presented primary overactive bladder resistant to first‐line treatments. Patients were excluded in case of secondary bladder, pelvic, or neurological condition. Patients were randomized between bilateral testing (n = 28) or unilateral testing (n = 27), to determine the best functional response before final implantation. The primary outcome was the rate of patients presenting at least 50% of clinical improvement at 1 month on urinary frequency, number of urge incontinence episodes or number of urinary urgency episodes. Symptom severity, implantation success rate, uroflowmetry, device tolerance, complications, and quality of life were also assessed. Results Fifty‐five patients have been included. The rate of patients presenting at least one significant clinical improvement at month 1 was 62% in the bilateral group versus 84% in the unilateral group (P = .0891), RR = 0.74 (0.51; 1.07). There was no significant difference between bilateral and unilateral groups in terms of improvement of urinary frequency (0% and 17%; P = .1115), number of urge incontinence episodes (52% and 63%; P = .4929) or number of urinary urgency episodes (57% and 74%; P = .2411). More complications were reported in the bilateral group than in the unilateral group (9 [47%] vs 4 [16%], respectively; P = .0239). Conclusion Systematic bilateral sacral neuromodulation testing before final implantation did not appear to increase success rate compared with unilateral stimulation in the treatment of overactive bladder.