The present study aimed to explore factors that contribute to the use of psychosocial support services among cancer outpatients in Japan and to understand the utilization process. Content analysis was conducted on interview data collected from 41 participants. We extracted 11 higher order categories and 33 sub-categories of triggers and elements that constituted the process of utilization, and 12 higher categories and 38 sub-categories that constituted barriers to utilization. Additionally, two patterns of utilization; utilization with and without intervention from others were identified. Trends of the higher categories were similar to the results of previous studies, and more detailed sub-categories were identified in the present study. This research indicated the need to develop approaches for evoking outpatients’ perceptions about their problems, improving the content and usage of support services, and changing patients’ attitudes toward support use to promote help-seeking behaviors.