This study aimed to investigate effects of the interior design of a counseling room on participants' self-disclosure and impressions of a counselor. The authors examined the effects of lighting and decorations. It tested four conditions crossing decorations (with or without home-like decorations) and type of lighting (bright or dim). Eighty undergraduate students (clients) were randomly assigned to one of the conditions and individually underwent a structured interview with an interviewer (a counselor) and then completed a questionnaire. The results showed that dim lighting yielded more pleasant and relaxed feelings, more favorable impressions of the interviewer, and more self-disclosure than did the bright lighting. However, the authors found no predominant pattern of the decorations. Thus, the pleasant and relaxed feelings related to dim lighting may well enhance the perceived attractiveness of a counselor and self-disclosure from clients. The results imply that interior design could influence communication and other relationships in counseling rooms.