Understanding and acting on online health information is increasingly a pre-requisite for patient self-care. Therefore, inadequate health literacy is a barrier to self-care among older adults with chronic illness. The goal of our study was to improve older adults’ comprehension of online health information. We extracted typical health texts from multiple credible health websites, and systematically improved the texts in terms of, content, language, organization and design. Results showed that older adults better understood the revised passages than the typical ones, in terms of their reading efficiency (time per unit of information uptake). Intervention benefits were greater for older adults with more domain-specific health knowledge, suggesting that knowledge facilitated the comprehension of health information in the revised texts. Implications for promoting older adults’ comprehension of health information are discussed.