Abstract Objective: To review evidence on the type, characteristics, and effect of Digital Health Interventions (DHIs) on medication adherence among older people. Methods: Articles were searched from inception to May 2025 in PubMed, Embase, CINAHL, Scopus, and Web of Science. Randomised and non-randomised studies were included if they: involved older people aged ≥65 years; applied any DHI(s); compared the intervention with a comparator group or baseline; and reported medication adherence as an outcome. Risk of bias was assessed using the Cochrane risk of bias tools, and certainty of evidence using GRADE (Grading of Recommendations, Assessment, Development and Evaluation). A narrative synthesis was conducted. Results: A total of 35 articles were included, most of which were randomised controlled trials (n=22). Risk of bias ranged from low to high, and certainty from very low to moderate. Nearly half of the studies (n=17) reported DHI/s improved medication adherence compared with control or baseline. Mobile apps (3/5), electronic reminders (3/3), social assistive robots (1/1), telenursing (1/1), and combined DHIs (2/2) showed the most promise. Interventions that used multiple functionalities and strategies to support behavior change (reminders or prompts) were most likely to improve adherence. The other DHIs had mixed results or no significant effects. Conclusions: While findings across DHIs varied, interventions incorporating tailored reminders, multicomponent features, and interactivity may have the potential to be more effective in improving medication adherence among older adults. Further research is needed to identify usage patterns and investigate the factors underlying differences in effectiveness.