The severe threat of misinformation and the rapid advancement of artificial intelligence technology have driven the development and application of AI-assisted judgment tools. To explore how younger and older adults understand and adopt AI-assisted advice for misinformation detection, this study extracted their mental models. This study recruited a total of 120 valid participants, including 60 younger participants and 60 older participants. By having the participants judge the credibility of information with the help of AI tools, we interviewed them about their reasons for adopting or rejecting AI-assisted advice and their understanding of how AI tools detect information. This study has several findings. First, younger participants were more likely than older participants to adopt AI-assisted advice. Second, three aspects have been identified in determining people’s strategies for adopting or rejecting AI-assisted advice. Third, compared with older participants, younger participants showed a better understanding of the dynamic detection process of AI tools. Key findings indicate that rejecting AI advice is easier than adopting it. Younger adults exhibit more complex mental models, integrating various AI-related factors, while older adults rely more on their own judgment and the AI’s results. These findings contribute to our understanding of age differences in adopting AI for information credibility judgments.