Digital health literacy is a basic requirement for the use of digital health solutions. However, it is not yet sufficiently present among users, so that appropriate programmes are needed to promote it. The aim of this study is to investigate the effect of online self-learning platforms on digital health literacy. In a two-armed randomised controlled trial (RCT) with n = 40, participants were assigned to an intervention group (IG) and a control group (CG). The eHealth Literacy Scale (eHEALS) and an adapted version were used to assess digital health literacy. The effect was compared to before and to the control group after using the online self-learning platform. After the intervention digital health literacy improved in the intervention group (p < .001) in both scores and was higher in eHEALS-Score (p = .047) and eService-Score (p = .000) than in the control group. The results indicate that digital services should become increasingly relevant for promoting digital health literacy in the population.