ImportanceAcupuncture is a promising therapy for irritable bowel syndrome (IBS), but the use of subjective scales as an assessment is accompanied by high placebo response rates.ObjectivesTo preliminarily test the feasibility of using US Food and Drug Administration (FDA)–recommended end points to evaluate the efficacy of acupuncture in the treatment of IBS.Design, Setting, and ParticipantsThis pilot, multicenter randomized clinical trial was conducted in 4 tertiary hospitals in China from July 1, 2020, to March 31, 2021, and 14-week data collection was completed in March 2021. Individuals with a diagnosis of IBS with diarrhea (IBS-D) were randomized to 1 of 3 groups, including 2 acupuncture groups (specific acupoints [SA] and nonspecific acupoints [NSA]) and a sham acupuncture group (non-acupoints [NA]) with a 1:1:1 ratio.InterventionsPatients in all groups received twelve 30-minute sessions over 4 consecutive weeks at 3 sessions per week (ideally every other day).Main Outcomes and MeasuresThe primary outcome was the response rate at week 4, which was defined as the proportion of patients whose worst abdominal pain score (score range, 0-10, with 0 indicating no pain and 10 indicating unbearable severe pain) decreased by at least 30% and the number of type 6 or 7 stool days decreased by 50% or greater.ResultsNinety patients (54 male [60.0%]; mean [SD] age, 34.5 [11.3] years) were enrolled, with 30 patients in each group. There were substantial improvements in the primary outcomes for all groups (composite response rates of 46.7% [95% CI, 28.8%-65.4%] in the SA group, 46.7% [95% CI, 28.8%-65.4%] in the NSA group, and 26.7% [95% CI, 13.0%-46.2%] in the NA group), although the difference between them was not statistically significant (P = .18). The response rates of adequate relief at week 4 were 64.3% (95% CI, 44.1%-80.7%) in the SA group, 62.1% (95% CI, 42.4%-78.7%) in the NSA group, and 55.2% (95% CI, 36.0%-73.0%) in the NA group (P = .76). Adverse events were reported in 2 patients (6.7%) in the SA group and 3 patients (10%) in NSA or NA group.Conclusions and RelevanceIn this pilot randomized clinical trial, acupuncture in both the SA and NSA groups showed clinically meaningful improvement in IBS-D symptoms, although there were no significant differences among the 3 groups. These findings suggest that acupuncture is feasible and safe; a larger, sufficiently powered trial is needed to accurately assess efficacy.Trial RegistrationChinese Clinical Trial Registry: ChiCTR2000030670