Background: The new curcumin derivative, Theracurmin® has a 27-fold higher absorption rate than the natural curcumin powder. Its pharmacologic actions include inhibition of the nuclear factor NF-κB, known to mediate the expression of inflammatory cytokines. We were interested to evaluate efficacy of Theracurmin® in patients with Crohn's disease (CD). Methods: Theracurmin® (360mg/day, n=20) or placebo (n=10) was administered to patients with active mild to moderate CD for 12 weeks. Efficacy assessment included clinical and endoscopic remission, healing of anal lesions, and blood levels of inflammatory markers. Findings: In the Theracurmin® group, significant reduction of clinical disease activity was observed at 12 weeks relative to week 0 (P=0.005). The clinical remission rates were 35%, 40%, and 40% at weeks 4, 8, and 12, respectively, significantly higher than in the placebo group (P=0.033, P=0.020, and P=0.020). Further, in the Theracurmin® group, significant healing of anal lesions (P=0.017) and endoscopic CD severity (P=0.032) were observed at weeks 8 and 12, respectively, relative to week 0. However, the mucosal healing rate at week 12 in the Theracurmin® group was 15.0%. No serious adverse event was observed in either group throughout our observation time. Interpretation: In this study, Theracurmin® in patients with active mild to moderate CD produced significant clinical and endoscopic efficacy together with a favourable safety profile. Trial registration: UMI15770 Funding Statement: Theracurmin® was a gift from Theravalues Corporation, Tokyo, Japan. The authors received no external funding for this study. Declaration of Interests: All authors acknowledge having no conflict of interest in connection with the publication of this manuscript. Ethics Approval Statement: At each institution, the study protocol was reviewed and approved by the committee on the Ethics of Clinical Trials involving human subjects. Further, the trial was conducted by adherence to the principles of Good Clinical Practice (GCP) and the ethical standards laid down in the 1964 Helsinki Declaration and its subsequent amendments. Similarly, informed consent was obtained from all patients after explaining the purpose of the study and the nature of the procedures involved.