Our research contributes mainly to two fields: one concerns the influence of the marketing department, and the other is the study of market orientation, especially research that views market orientation as an information process. Motivated by discussion of marketingʼs declining influence within the company, we investigated the marketing departmentʼs credibility and influence in Japanese firms, where it has traditionally wielded weaker power than in Western firms. From intensive interviews with marketing professionals, we find that the lack of credibility of market information is a crucial factor that undercuts the influence of the marketing department. The results of our questionnaire survey indicate that the credibility of market information has a more positively significant effect on market orientation than does marketing influence.