This study hypothesizes and empirically tests the influence of involvement of (1) frontline employees and (2) top managers in ideation process on healthcare service innovation quality. Based on data from 168 service innovation projects in Dutch healthcare organizations, the empirical results indicate that frontline employee involvement and top management involvement in, respectively, idea generation and idea application both improve the quality of healthcare service innovation. We find that the positive effect of frontline employee involvement is stronger under the condition of higher service innovativeness. In the direct relationship of top management involvement and healthcare service innovation quality, our data do not show such a moderating effect. The key and general managerial implication of the findings is that healthcare organizations are inspired to involve frontline employees in the idea generation processes and involve top managers in the idea application processes of service innovation projects, in order to improve innovation quality.