Background Current clinical decision support systems (CDSSs) for antimicrobial stewardship programs (ASPs) are guideline- or expert-driven. They are focused on (clinical) content, not on supporting real-time workflow. Thus, CDSSs fail to optimally support prudent antimicrobial prescribing in daily practice. Our aim was to demonstrate why and how participatory development (involving end-users and other stakeholders) can contribute to the success of CDSSs in ASPs. Methods A mixed-methods approach was applied, combining scenario-based prototype evaluations (to support verbalization of work processes and out-of-the-box thinking) among 6 medical resident physicians with an online questionnaire (to cross-reference findings of the prototype evaluations) among 54 Dutch physicians. Results The prototype evaluations resulted in insight into the end-users and their way of working, as well as their needs and expectations. The online questionnaire that was distributed among a larger group of medical specialists, including lung and infection experts, complemented the findings of the prototype evaluations. It revealed a say/do problem concerning the unrecognized need of support for selecting diagnostic tests. Conclusions Low-fidelity prototypes of a technology allow researchers to get to know the end-users, their way of working, and their work context. Involving experts allows technology developers to continuously check the fit between technology and clinical practice. The combination enables the participatory development of technology to successfully support ASPs.