Okara is a byproduct of soymilk manufacturing and a rich source of protein and dietary fiber. We investigated whether okara intake improves the habit of defecation in young Japanese women (n = 52) with self-reported constipation. Subjects were categorized into placebo and test groups, who ingested soymilk (0.1 g fiber/meal) and okara (4.1 g fiber/meal) soups, respectively, every day for breakfast, for 2 weeks. Subjects' body composition, bowel movement frequency per week, and constipation assessment scale (CAS) and brief-type self-administered diet history questionnaire scores were assessed at baseline and after the intervention (Analysis 1). Further, subjects' bowel movement frequency per week and CAS scores were assessed during the 2-week follow-up (Analysis 2). There were no significant differences in age, anthropometric characteristics, nutrients intake, frequency of bowel movements per week, and total CAS scores between the placebo and test groups at baseline. After intervention, the total CAS score was significantly lower in the test group than in the placebo group. Moreover, the difference in the total CAS scores between baseline and after intervention was lower in the test group than in the placebo group, although not significant. The weekly frequency of bowel movement significantly increased for both placebo and test groups. The test group reported reduced abdominal bloating 2 weeks after the intervention, but the placebo group did not. The findings suggest that okara is effective in increasing the frequency of bowel movements and improving defecation habit in young women with self-reported constipation.