Introduction: This study aimed to develop and validate a diet consultation tool that assesses the perceived benefits and barriers of vegetable consumption attached to the stage of change in Japanese adults. Methods: A web-based survey was conducted among university and vocational school students, medical staffs, and local residents in the Aichi, Osaka, and Kyoto prefectures of Japan between September 2017 and January 2018. Participants comprised of 379 adults aged 20–70 years (mean age: 30.5±12.6 years; men: 21.4%). The scale for decisional balance of vegetable consumption contained 15 benefit items and 15 barrier items. The internal consistency of the scale was examined using Cronbach’s alpha and construct validity was examined using an exploratory factor analysis with Promax rotation. Results: The developed questionnaire had 12 items across two domains for benefits and 12 items across three domains for barriers that were structured with high internal consistencies (Cronbach’s alpha: 0.82, 0.79, 0.82, 0.76 and 0.76, respectively). The intraclass correlation coefficient in the test-retest reliability study was substantial (0.77). We found a very clear association between decreasing barrier score with increasing vegetable consumption and progress in the stage of change. The decisional balance score (benefits score minus barriers score) was positively correlated with the number of vegetable servings as an external parameter (Spearman’s correlation: 0.461; p<0.001). Conclusion: The developed questionnaire was a valid, reliable, and useful tool for diet consultants to assess the perceived benefits and barriers of vegetable consumption in Japanese adults.