Background <p>The global rise in population aging and the increasing burden of non-communicable diseases demand scalable, cost-effective strategies to support healthy aging. Conversational agent-based interventions, which deliver personalized guidance through interactive dialogue, offer a promising yet underexplored approach to promoting lifestyle behavior change among older adults. Thus, the purpose of this study is to systematically review the characteristics, acceptability, and effectiveness of conversational agent-based interventions for lifestyle behavior modification in older adults, and to identify key design and research considerations for advancing this emerging field.</p> Methods <p>A comprehensive search of MEDLINE, EMBASE, PsycINFO, and CINAHL databases was conducted from inception to February 28, 2025. Studies evaluating behavior-related outcomes of conversational agent-based interventions targeting lifestyle modifications in older adults were included. Methodological quality was appraised using the Quality Assessment Tool for Studies with Diverse Designs (QATSDD).</p> Results <p>Six studies met the inclusion criteria, comprising four randomized controlled trials, one quasi-experimental study, and one observational cohort study. Most conversational agents were frame-based, computer-delivered, and embodied, featuring button-based text inputs and integrating theory-driven relational and persuasive strategies. Although evidence suggested that these interventions were largely feasible and acceptable to older adults, their efficacy in promoting physical activity, diet, and other health outcomes remains inconclusive, likely due to limited evidence, varied designs, and inconsistent outcome measures and statistical methods.</p> Conclusions <p>This review identified key features of conversational agents designed to promote lifestyle behavior change among older adults and highlighted existing design limitations that may undermine user engagement and effective adoption of these technologies. To fully realize and leverage the potential of conversational agents in supporting healthy aging, it is crucial to focus on user-friendly designs, detailed reporting of the underlying theories and design processes, and thorough evaluations of relevant health outcomes.</p> Systematic review registration <p>PROSPERO CRD420251039283.</p>