Most hospital websites have not been developed in collaboration with patients and, therefore, rarely take into account the preferences and abilities of older patients. This study describes the systematic redesign of an existing hospital website in a co-design process with patients and professional stakeholders (e.g. researchers, physicians, nurses, department heads, policymakers, website designers), with the aim to make it more user-friendly for older patients with colorectal cancer (CRC). The redesign process consisted of three phases, where (I) both existing content and design were evaluated among CRC patients; (II) a prototype website was developed based on these insights; which (III) was evaluated again before making final adjustments. Mixed research methods were used for the redesign process. Specifically, insights from existing literature, outcomes from qualitative and quantitative empirical studies conducted by our team, and expert knowledge from relevant stakeholders, were collected and discussed in multidisciplinary consensus meetings, and served as input for the redesigned website. While the existing website was evaluated poorly, the qualitative evaluation of the prototype website in phase 3 showed that the newly redesigned website was usable for older CRC patients. A practical roadmap on how to collaboratively redesign and optimise existing eHealth tools to make them suitable for and operational in clinical settings is provided.