Diarrhea-predominant irritable bowel syndrome (IBS-D)-like symptoms are distressing for patients with quiescent Crohn’s disease (qCD) and worsen their quality of life. In the present study, we assessed the effect of the probioticBifidobacterium bifidumG9-1 (BBG9-1) on the intestinal environment and clinical features in patients with qCD. Eleven patients with qCD, who met the Rome III diagnostic criteria for IBS-D, received BBG9-1 (24 mg) orally three times daily for 4 weeks. Indices of the intestinal environment (fecal calprotectin level and gut microbiome) and clinical features (CD/IBS-related symptoms, quality of life and stool irregularities) were evaluated before and after treatment. Treatment with BBG9-1 tended to reduce the IBS severity index in the studied patients (p= 0.07). Among gastrointestinal symptoms, abdominal pain and dyspepsia tended to be improved by the BBG9-1 treatment (p= 0.07 andp= 0.07, respectively), and IBD-related QOL showed a significant improvement (p= 0.007). With regard to mental status, the patient anxiety score was significantly lower at the endpoint of BBG9-1 treatment than at the baseline (p= 0.03). Although BBG9-1 treatment did not affect the fecal calprotectin level, it suppressed the serum MCP-1 level significantly and increased the abundance of intestinalBacteroidesin the study patients. The probiotic BBG9-1 is able to improve IBD-related QOL with a reduction of anxiety score in patients with quiescent CD and IBS-D-like symptoms.